Locksmith Glossary

Active Leaf: In a pair of doors, the door or doors in which the latching device is installed; also referred to as an Active Door.

AHJ: (abbr.) Authority having Jurisdiction.
All-section Key Blank: The key section that enters all the keyways of a multiplex key system. ALOA: Associated Locksmiths of America, Inc.

Alternating Parity: Most often describes the type of mathematical progression employed to develop master key systems. Parity refers to the bitting depths, “odd” or “even” numbers. In an alternating parity system, the bitting depths in any given bitting position can be odd or even numbered depths; sometimes called a “one-step” system.

Americans with Disabilities Act: This is a US federal law dealing with minimum standards of building accessibility, as well as other issues affecting individuals with disabilities.

Annunciator: A device that produces an audible and/or visible indication of light and/or noise, or a verbal message.

ANSI: (abbr.) American National Standards Institute, Inc.

ANSI Cut-out: A standardized cut-out for hardware furnished on many rated and non-rated doors and frames.

Anti-friction Latch: A device incorporated into the latch bolt of a lock for reducing friction between bolt and strike.

Associated Change Key: A change key which is related directly to particular master key(s) through the use of constant cuts.

Associated Master Key: A master key that has particular change keys related directly to its combination via the use of constant cuts.

Astragal (Overlapping): A vertical moulding that extends the full height of the door leaf and is applied to a door or pair of doors at their meeting edges. The astragal closes the clearance gap for the purpose of providing a weather seal, minimizing the passage of light between the doors, retarding the passage of smoke and flame during a fire, or maintaining security. Some types of astragals are flat pieces of aluminum, steel, or wood. Some astragals are designed to wrap around the lock stile of the door. Overlapping astragals are not permitted to be used on pairs of doors that are required to swing in the direction of egress travel. (See also Astragal [Split])

Astragal (Overlapping & Interlocking): A set of vertical mouldings that extend the full height of the door and is fastened to a door and jamb or a pair of doors that interlock for increased security from a forced entry attack.

Astragal (Split): A vertical molding attached to the meeting edges of each of the leaves of a pair of doors, for protection against weather. The split feature permits both leaves to be active. Split astragals can be surface-mounted, semi-mortised or full-mortised in the vertical edge of the doors. Split astragals are available with brush, pile, silicone, neoprene, or vinyl inserts to seal the gap between the meeting stiles in pairs of doors.

Back Check: The resistance provided by a door closer as the door is opened.

Backset: The distance from the vertical centreline of the leading edge of a door to the centerline of the lock cylinder measured horizontally.

Barrel Bolt: A surface-mounted slide bolt with a cylindrical shape.

Barrier-free: Refers to ensuring accessibility for seniors and people with disabilities.

Bell Crank: A mechanical device using a pivoting action to change the direction of a mechanical force or motion.

Bevel (of a door): The pitch on the leading edge of a door that allows clearance for closing.
Bevel (of a lock): The pitch of the face designed to match the bevel of a door. Some locks have an adjustable bevel.

Bezel: A threaded collar commonly used to secure certain cylinder or lock assemblies.

BHMA: (abbr.) Builders Hardware Manufacturers’ Association

Bible: The portion of the cylinder shell that normally houses the pin chambers, especially those of key- in-knob cylinders or certain rim cylinders.

Binary-type Cylinder or Lock: A cylinder or lock with a combination that only allows for two bitting possibilities in each position.

Bit: The part of the key that serves as the blade; usually for use in a warded or lever tumbler lock. Bit Key: A key with one or more projecting bits.

Bitting: The number(s) that represent(s) the dimensions of the key cuts OR the actual cut(s) or combination of the key.

Bitting Depth: The depth of a cut that’s made into the blade of a key.

Bitting Increment: Within a lock manufacturer’s key cutting specifications, the bitting increment is the uniform measurement from one successive bitting depth to the next i.e. with a bitting increment of .018″ and if a #0 cut measures .320″, a #1 cut will measure .302″, a #2 .284″, etc.

Bitting List: A list of all key combinations used within a system. The combinations are most often arranged in order of the blind codes, direct codes and/or key symbol.

Blank: See Key Blank

Blind Code: A designation, unrelated to the bitting, assigned to particular a key combination for future reference when additional keys or cylinders may be needed.

Block Master Key: The level-one master key that operates one block of changes in a key bitting array of a standard progression format master system.

Bolt: Any moveable projection that blocks the movement of one object in relation to another. Boltworks: The combination of bars, rods, plates and linkages in a safe door designed to hold the door in the locked or unlocked position depending on the status of the lock itself OR any part of a lock other than a cylinder, turn piece, or operating handle that affects the movement of, or the ability to, move the bolt.

Bond Box: The removable container within a safe deposit box compartment.

Bore: To make a hole in or through, especially with a revolving tool. (See “Edge Bore” and “Cross Bore”)

Bored Locks: Any lock that requires a hole cross-bored through the door into which the lock is installed.

Building Master Key: A key that operates all or most master keyed locks in a given building.

Bump Key: A lock picking key with uniform steeples between cuts that is forced further into the lock via impact.

Cam: A lock or cylinder component that transfers the rotational motion of a key or cylinder plug to the bolt works of a lock OR the bolt of a cam lock.

Cam Lock: A complete locking assembly in the form of a cylinder whose cam is the actual locking bolt. Cane Bolt: A surface-mounted deadbolt designed to be moved by hand via a 90o bend in the bolt that serves as a handle.

Case: The housing of a lock, usually metal, that contains the lock mechanism.

Case Harden: To harden the surface of an iron-based alloy by carburizing and heat treatment, leaving the interior tough and ductile.

Center Case: The active chassis of a touch-bar or cross-bar exit device. Chamber: Any cavity in a cylinder plug and/or shell that houses the tumblers.

Change Index: The point on a dial ring to which the old and new combinations must be dialed when changing the combination.

Change Key: A key that operates only one cylinder or one group of keyed-alike cylinders in a keying system OR any device used to mechanically or electronically allow resetting of certain key or combination locks. (See also “Reset Key”)

Chassis: The part of a cylindrical lockset that contains the actuating mechanism and has a means for mounting trim and a bolt

Cloner: A device for reading and writing data to electronic or hybrid keys

Cloverleaf Cam: A style of mortise cylinder cam with three lobes: a ball-shaped longer center and angular projections on either side.

Code Book: A book in which indirect key codes can be referenced to their corresponding key bitting specifications.

Code Key: A key cut to a specific code rather than duplicated from a pattern key; may or may not conform to the lock manufacturer’s specifications.

Column Master Key: The level two master key that operates all changes in a column of blocks in a key bitting array of the standard progression formation.

Combination: The group of numbers representing the bitting of a key and/or the tumblers of a lock or cylinder.

Compensate Drivers: The action of selecting longer or shorter pins, depending on the length of the rest of the pin stack, in order to achieve a uniform pin stack height. (See also Graduated Drivers)

Concealed Vertical Rod Exit Device: A vertical rod exit device with rods and header/threshold bolts that are concealed within the door.

Constant Cut: Any bitting(s) identical in corresponding positions from one key to another in a keying system. These keys are usually grouped together within a given level of keying and/or linked with keys of other levels. (See also Rotating Constant)

Constant Parity: Usually used to describe the type of mathematical progression employed to develop a master key system. “Parity” refers to the bitting depths, i.e. “odd” or “even” numbers. In a constant parity system, all bitting depths in a given bitting position are either all odd or all even number depths; sometimes called a “two-step” system.

Continuous Duty: An electrical term referring to the sustainable application of power over extended periods of time.

Control Key: A key with a sole purpose to remove and/or install an interchangeable or removable core OR a bypass key used to operate and/or reset some combination type locks OR a key that permits disassembly of some removable cylinder locks.

Control Sleeve: The part of an interchangeable or removable core retaining device that surrounds the plug.

Control Lug: The part of an interchangeable or removable core retaining device that locks the core into its housing.

Controlled Cross Keying: A condition in which two or more different keys of the same level of keying and under the same higher level key(s) operate one cylinder by design; eg. XAA1 operated by AA2 (but not XAA1 operated by AB1).

Note: This condition could severely limit the security of the cylinder and the maximum expansion of the system when more than a few of these different keys operate a cylinder OR more than a few differently cross-keyed cylinders per system are required.

Core: A complete unit, often with a figure 8 shape, that usually consists of the plug, shell, tumblers, springs, plug retainer and spring cover(s); used primarily in removable and interchangeable core cylinders and locks.

Cremone Bolt: A surface-mounted, top and bottom locking, deadbolt mechanism operated in unison by a central handle; often made from decorative cast iron.

Cross Bore: Term referring to a hole drilled through the face of a door into which a lock is installed; used to differentiate between this hole and the edge bore.

Cross Keying: The deliberate process of keying a cylinder (usually in a master key system) to two or more different keys that would not normally be expected to operate together. (See also Controlled Cross Keying and Uncontrolled Cross Keying)

Cruciform: Of or pertaining to a key section or keyway; usually resembling a plus sign (+) or the letter “X”.

CSA: (abbr.) Canadian Standards Association
Current Transfer: A wiring device used to supply electrical current from a door jamb to door-mounted devices. Current transfers are in the form of door loops, concealed loops and electric transfer hinges. Cut: To make cuts into a key blade.

Cut Angle: A measurement, usually expressed in degrees, of the angle between the two sides of a key cut.

Cut Edge: The portion of the key blade that contains the cuts.

Cut Key: A key that has been bitted or combinated.

Cut Root: The bottom of a key cut.

Cut Root Depth: The measurement from the bottom of a cut in a key to the bottom of the key’s blade.

Cut Root Shape: The shape of the bottom of a key cut. It may have a flat or a radius of a specific dimension or be a perfect “V”.

Cutter: The part of a key machine that makes the cuts into the key blank.

Cutter Guide: That part of a key machine that follows the cuts of a pattern key or template during duplication.

CVR: (abbr.) Concealed vertical rod exit device

CVC: (abbr.) Concealed vertical cable exit device

Cylinder : The complete operating unit; usually consisting of the plug, shell, tumblers, springs, plug retainer, a cam/tailpiece or other actuating device, and all other required operating parts.

Cylinder Blank: A dummy cylinder with a solid face and no operating parts.

Cylinder Clip: A spring steel ‘u-shaped’ device used to secure some types of cylinders.

Cylinder Collar: A plate or ring installed under the head of a cylinder to improve appearance and/or security. (See also Cylinder Guard)

Cylinder Guard: A cylinder collar designed to protect the cylinder from prying and wrenching attacks. Cylinder Key: A broad generic term including virtually all pin and disc tumbler keys.

Cylindrical Lock: A bored lockset with latch or bolt locking mechanism contained in the portion installed through the cross-bore.

Day Gate: A barrier used to restrict passage during normal business hours, normally used at a vault entrance

Deadbolt: A bolt requiring a deliberate action to extend, and that resists end pressure in the unlocking direction when fully extended.

Deadlatch: A spring latch designed with an anti-shim feature that resists attempts to push it back into the retracted position when the door is closed and the deadlocking feature is activated by its position in the strike.

Deadlock: A lock that incorporates a deadbolt.

Deadlocking: Pertaining to any feature that, when fully engaged, resists attempts to move the latch or bolt in the unlocking direction through direct pressure.

Declining Step Key: A key with cuts progressively deeper from bow to tip.

Decode: To determine a key combination by physical measurement of a key and/or cylinder parts.

Degree of Rotation: A specification for the angle at which a cut is made into a key blade as referenced from the perpendicular eg. right (R or 2), left (L or 1) or center (= perpendicular) (C). This specification is typically used for high-security keys.

Delayed Action Closer: A door closer function with a specific hold-open interval before it moves a door toward the latching position.

Delayed Egress: An exit that will not open until a specified amount of time has elapsed after actuation.

Department Master Key: A master key operating all or most master keyed locks of a given department.

Depth Key Set: A set of keys used to make a code original key on a key duplicating machine to a lock manufacturer’s given set of key bitting specifications. Each key is cut with the correct spacing to one depth only in all bitting positions, with one key for each depth.

Derived Series: A series of blind codes and bittings directly related to those of another bitting list. DHI: (abbr). Door and Hardware Institute

Dial: The typically rotatable member of a combination lock be used to differentiate locations on the combination wheels and cause operation of the lock OR the act of turning or rotating a dial.

Dial Ring: An escutcheon for a combination lock dial. Dimple: A key cut in a dimple key. (See also Dimple Key)

Dimple Key: A key with cuts drilled or milled into its blade surfaces. The cuts normally do not change the blade silhouette.

Direct Code: A designation assigned to a particular key that includes the actual key combination. Direct Drive: Of, or pertaining to, a combination lock with the drive cam mounted on the dial’s spindle shaft.

Disc Tumbler: A flat tumbler that must be drawn into the cylinder plug by the proper, ensuring that none of its extremities extend into the shell OR. a flat, usually rectangular tumbler with a gate that must be aligned with a sidebar by the proper key; also referred to as a wafer tumbler.

Display Key: A special change key in a hotel master key system allowing access to one designated guest room, even if the lock is in the shut-out mode. It may also act as a shut-out key for that room.

Dogging: To fix an exit device or latch lock in a position where the latch remains retracted.

Dogging Cylinder: A key-operated cylinder used to dog an exit device.

Dogging Device: In an exit device, a mechanism used to temporarily disable the latch from locking.

Dogging Key: Usually a hex wrench with a special head for convenience; used to activate the dogging mechanism on a panic exit device.

Dogging Key 001

Dogging Key 001

Hex Dogging Key 001

Hex Dogging Key 001




Dogging Screw: A screw used to dog an exit device.

Door Closer: A device designed to regulate the action of a door automatically by various means.

Door Closer Arm: The arm is the connection between the door and the closer, or the jamb and the closer.

Door Coordinator: A piece of hardware used on a pair of doors in order to hold the active door open until the inactive door is closed.

Door Holder: Devices designed to maintain a door in the open position.

Door Loop: A hollow metal flexible cable with a mounting plater on each end, designed to carry electrical cable from the door jamb to the door. (See also Current Transfer).

Door Pull: A handle mounted onto the door used to open the door.

Door Silencer: A bumper installed in the jamb stop to quiet the closing of a door.

Door Thickness: The dimension of a door measured from side-to-side along one edge.

Door Viewer: A device with one or more lenses, mounted in a door at eye level, allowing a limited view from the interior to the exterior of the door.

Door Schedule: See Hardware Schedule

Double-acting Closer: A door closer designed to be used on a double-acting door Double-acting Door: A door that may be pushed open from either side.

Double-acting Hinge: A hinge permitting movement of a door in either direction from the closed position.

Double-bitted Key: A key bitted on two opposite surfaces. (See also Single-bitted Key)

Double Cylinder Lock: A type of lock with two cylinders; one on the inside of the door and one on the outside, to activate the locking mechanism.

Double Pin: To place more than one master pin in a single pin chamber.

Drill Point: The exact measurement of the location used to drill a locked-up container to create an opening.

Drive-in: Pertaining to a latch or bolt with a round face.

Driver Spring: A spring placed on top of the pin stack to exert pressure on the pin tumblers.

Drop In: The gate area of the drive cam where the lever nose drops into; usually identified with a corresponding number on the dial.

Dual Custody: A function designed to require the presence of two persons with two different keys, combinations or codes to operate the same device.

Dummy Cylinder: A non-functional facsimile of a rim or mortise cylinder used for appearance only, usually to conceal a cylinder hole.

Dummy Trim: A non-active trim applied for aesthetic purposes.

Duplicate: To copy

Duplicate Key: A key reproduced from a pattern key.

Dust Box: A small box, usually made of plastic or metal, which fits behind a strike plate for the purpose of preventing debris from inside the door jamb, from entering the strike hole.

Dust Cover: A device designed to prevent foreign matter from entering a mechanism through the keyway.

Dust-proof Cylinder: A cylinder designed to prevent foreign matter from entering either end of the keyway.

Dust-proof Strike: A typically floor-mounted strike that has a spring-loaded internal plunger designed to keep the receptacle free of dust and debris.

Dutch Door: A door consisting of two separate leaves, an upper leaf and a lower leaf, that operate independently. The lower leaf frequently has a service shelf at its top.

Edge Bore: A hole drilled into the edge of a door in order to install the latch and/or bolt mechanism of a cylindrical or tubular lock.

EEPROM: (abbr.) Electrically erasable, programmable, read-only memory

Effective Plug Diameter: The dimension obtained by adding the root depth of a key cut to the length of its corresponding bottom pin, which establishes a perfect shear line. This is not necessarily the same as the actual plug diameter.

Egress: To exit

Ejector Hole: A hole found on the bottom of certain interchangeable cores under each pin chamber, that provides a path for the ejector pin.

Ejector Pin: A tool that drives all the elements of a pin chamber out of certain interchangeable cores.

Emergency Key: The key or tool that operates a privacy function lockset.

Emergency Master Key: A special master key that usually operates all guest room locks in a hotel master key system at all times, even in the shut-out mode. This key may also act as a shut-out key.

EMK: (abbr.) Emergency master key

End Case: Component of some exit devices which fastens to the door, near the hinge side, and provides an anchor point for that end of the bar. (See also Center Case) ENG: (abbr.) Symbol for an engineer’s key.

Engineer’s Key: A selective master key used by maintenance personnel to operate many locks under different master keys in a system of three or more levels of keying.

Entrapment Cylinder: A lock cylinder designed to trap a key that is inserted into it.

Escutcheon: A surface-mounted trim enhancing the appearance and/or security of a lock installation.

Exit Alarm: An annunciator that signals the opening of an exit door.

Exit Device: A door lock/latch mechanism that releases in the direction of exit travel via a bar or panel extending across the major width of the door.

Exit Door: A door that has no provision for ingress OR a door that fills some or all of the code requirement for safe egress of the occupant load from a building or portion of a building.

Exit Only: Hardware designed to secure an opening in such a way as to permit exit at all times but prevent entry at all times.

Extension Link: A device used to extend the backset of a spring latch or dead latch.

External 2 Track: A sidewinder key that is cut one place on each flat side of the key, flat to edge, creating 2 tracks on the key.

External 4 Track: A sidewinder key that’s cut in 2 places on each flat side of the key, flat to edge, creating 4 tracks on the key.

External Relocking Device: A device outside the lock case that prevents the safe door from being opened an attack. Typically two types are used, active and passive.

Extractor Key: A tool that normally removes a portion of a two-piece key or blocking device from a keyway.

Face Plate: Lock cover plate exposed in the edge of a door.

Factory Original Key: The cut key furnished by the lock manufacturer for a lock or cylinder.

Fail Safe: Functional description of an electric locking device that is unlocked when not energized. (eg.) in the event of a power failure), the device is safe (exit is still possible) See also “Fail Secure”.

Fail Secure: Functional description of an electric locking device which is locked when not energized. (eg.) in the event of a power failure), the device is secure. (See also Fail Safe)

False Gate: A gate in a part of the operating mechanism, that is not formed deeply enough to allow operation of the lock.

Fence: A projection on a lock bolt which prevents movement of the bolt unless it can enter gates of properly aligned tumblers OR any locking element other than a sidebar or shackle designed to enter a tumbler’s gate.

Finish: A material, coloring and/or texturing specification.

Fire Safe: An insulated safe designed to protect its contents from fire, rather than burglary.

Fire Door: A door constructed to provide a specific degree of fire protection.

Fire Door Assembly: Any combination of a fire door, frame, hardware and other accessories, that together provide a specific degree of fire protection to the opening.

Fire Exit Hardware: These are exit devices, which may legally be installed, on fire doors; distinguishable from other exit devices because they’re labeled for fire and have no means of locking the latch in a retracted position.

Fire Separation: Construction designed to limit the spread of fire in a structure.

Fireman’s Key: A key to override normal operation of elevators, bringing them to the ground floor.

First Generation Duplicate: A duplicated key from a factory original key or a code original as a pattern.

First Key: Any key produced without the use of a pattern key.

Five Column Progression: A process wherein key bittings are obtained by using the cut possibilities in five columns of the key bitting array.

Flexible Head Mortise Cylinder: An adjustable mortise cylinder that can be extended against spring pressure to a slightly longer length.

Floor Master Key: A master key that operates all or most master keyed locks on a particular floor of a building.

Floor Safe: A safe designed for mounting below floor level with the top surface flush with the finished floor; usually built into a concrete floor.

Flush Bolt: A locking bolt that, when installed within a door, is flush with the edge or face of the door. Fly: The part of a combination wheel pack or a drive cam that makes contact with a similar part on an adjacent wheel in the wheel pack and causes it to turn.

Follower: A tool used in the disassembly of pin tumbler cylinders, allowing for the removal of the cylinder plug while retaining the top pins, springs, and/or other components within the shell. The follower is so called because it is used to “follow” the plug as it is being removed.

Forbidden Zone: On a combination lock dial, a range of marks within which the last item of the combination must not be set to provide for proper lock operation.

Four Column Progression: A process wherein key bittings are obtained by using the cut possibilities in four columns of the key bitting array.

Front Drive: Of or pertaining to a combination lock with the drive cam located between the dial and the wheel pack

Function: A set of operating features for a particular type of lock or exit device that make it suitable for a specific application. The function is designated by a classification name or standards reference number. See ANSI or BHMA for a specific listing.

Fusible Link: A metal or plastic component designed to melt in the event of elevated heat, thereby releasing an attached device, such as a door closer hold-open or a relocking device.

Gate: A notch cut into the edge of a tumbler to accept a fence or sidebar. GGGMK: (abbr.) Great great grand master key (See below)

GGMK: (abbr.) Great grand master key (See below)

GMK: (abbr.) Grand master key (See below)

Ghost Key: A unintened key that opens one or more locks. Usually the result of a poorly designed Master Key System or improperly keyed lock.

Glass Relocker: A device employing a frangible plate intended to permanently incapacitate a security container’s normal opening mechanism if activated by physical attack on the container.

Graduated Drivers: A set of top pins of different lengths. Usage is based on the height of the rest of the pin stack, in order to achieve a uniform pin stack height. (See also Compensate Drivers)

Grand Master Key: The key that operates two or more separate groups of cylinders; each is operated by a different master key.

Grand Master Key System: A master key system with three levels of keying.

Grand Master Keyed: A cylinder which is to be keyed into a grand master key system.

Great Grand Master Key: The key that operates two or more separate groups of cylinders, each is operated by a different grand master key.

Great Grand Master Key System: A master key system with four levels of keying. Great Grand Master Keyed: A cylinder keyed into a great grand master key system.

Great Great Grand Master Key: The key that operates two or more separate groups of cylinders, each operated by different great grand master keys.

Great Great Grand Master Key System: A master key system with five or more levels of keying.

Great Great Grand Master Keyed: Of a pertaining to a lock or cylinder which is (or is to be) keyed into a great great grand master key system.

Guard Key: A key used in conjunction with a renter’s key to unlock a safe deposit lock. It is usually the same for every lock within the installation. The term “Guard Key” is typically used in reference to double-nose SD locks, while the term “prep key” identifies a key having the same function on single- nose SD locks. (See also Prep Key and Renter’s Key)

Guest Key: A key in a hotel master key system that’s normally used to unlock only the one guest room for which it was intended, but will not operate the lock in shut-out mode.

Guide: See Cutter Guide

Hand of Lock: The right or left hand the lock is presently set to, or what hand is required.

Handed: A term to indicate that a lock or door hardware product is intended for use on a specific hand of door, and cannot be used on any other hand of door, at least, not without some adjustment.

Hard Plate: A drill resistant metal plate, typically mounted under a lock in a safe to resist a drilling attack.

Hardware Schedule: A detailed list of the door hardware used on a particular job; includes the door sizes, locations, types of hardware, manufacturers, finishes, sizes and more . It should also include a keying schedule specifying how each locking device must be keyed.

Hasp: A hinged metal strap designed to be passed over a staple and secured in place.
Heel (of a padlock shackle): The part of a padlock shackle that is retained in the case when in the ‘unlocked’ position.

Heel & Toe Locking: A padlock with locking dogs at both the heel and toe of the shackle.

High Security Cylinder: A cylinder that offers a greater degree of resistance to any or all of the following: picking, impressioning, key duplication, drilling or other forms of forcible entry.

High Security Key: A lock operating device that offers additional defense against its duplication, and/or provides integral features precluding bypass/neutralization of a lock.

High Security Locks: Locks designed to resist unauthorized entry and provide a significant amount of key control.

Hinge: The joint on which a door or gate swings.

Hold Open: A function of a door closer, or separate hardware device that allows the door to be retained in an open position.

Hold Open Cylinder: A cylinder provided with a special cam that will hold a latch bolt in the retracted position when set by the key.

Holding Fixture: A device that holds cylinder plugs, cylinders, housing, and/or cores to facilitate the installation of tumblers, springs and/or spring covers.

Hollow Core Door: A door with an empty interior (except for rails) that holds the outer two sheets together.

Hollow Driver: A top pin hollowed out on one end to receive the spring; typically used in cylinders with extremely limited clearance in the pin chambers.

Horizontal Group Master Key: The two pin master key for all combinations listed in all blocks in a line across the page in the standard progression format.

Housekeeper’s Key: A selective master key in a hotel master key system that can operate all guest and linen rooms and other housekeeping areas.

Housing: The part of a locking device designed to hold a core.

Hub: The part of a lock or latch that is turned by the knob or handle to withdraw the bolt or latch.

Impression: The mark made by a tumbler on its key cut OR to fit a key by the impression technique.

Impression Technique: A means of fitting a key directly to a locked cylinder by manipulating a blank in the keyway and cutting the blank where the tumblers have made marks.

Inactive Leaf: In a pair of doors, the door that is secondary in usage and is normally locked by surface or flush bolts and is not key-controlled. Also referred to as an “Inactive Door”.

Incidental Master Key: A key cut to an unplanned shear line created when the cylinder is combinated to the top master key and a change key.

Increment: See Bitting Increment

Indicator: A device that provides visual evidence of a deadbolt that is extended or a lock that is in shut-out mode.

Indirect Code: A designation, unrelated to the bitting, assigned to particular key combination for future reference when additional keys or cylinders may be needed. Example: Ford Key Code FA2345 is cut on the code machine as “22104”

Individual Key: An operating key for a lock or cylinder that is not part of a keying system. Interchange: See Key Interchange

Interchangeable Core: A key removable core that can be used in all or most of the core manufacturer’s product line. No tools (other than the control key) are required for removal of the core.

Interlocking Pin Tumbler: A type of pin tumbler designed to be linked together with all other tumblers in its chamber when the cylinder plug is in the locked position.

Internal 4-Track: A sidewinder key cut with a centre cut in the middle of the flat of the key on each side on the with 2 combinations on each side of the cut; hence the name 4-track.

Jumbo Cylinder: A rim or mortise cylinder of 1 1/2″ diameter.
K: (abbr.) Symbol for “keys” used after a numerical designation of the quantity of keys requested to be supplied with the cylinders: e.g. 1k, 2k, 3k, etc. It is usually found in hardware/keying schedules.

KA: (abbr.) Keyed alike

KA/2, KA/3, etc.: Symbol used to indicate the quantity of locks or cylinders in keyed alike groups. These groups are usually formed from a larger quantity: eg. 30 cylinders KA/2. KA1, KA2, etc. Symbol indicates that all cylinders so designated are, or are to be, operated by the same key(s). The numerical designation indicates the keyed alike group or set.

KBA: (abbr.) Key bitting array KD: (abbr.) Keyed different

Key: A properly combinated device that is, or most closely resembles, the device specifically intended by the lock manufacturer to operate the corresponding lock.

Key Bitting Array: A matrix (graphic) display of all possible bittings for change keys and master keys as related to the top master key.

Key Bitting Punch: A manually-operated device that stamps or punches the cuts into the key blade, rather than grinding or milling them.

Key Bitting Specification: The technical data required to bit a given (family of) key blank(s) to the lock manufacturer’s dimensions.

Key Blank: Any material manufactured to the proper size and configuration that allows its entry into the keyway of a specific locking device. A key blank has not yet been cut.

Key Change: The combination of cuts in a key that enable it to operate the lock for which it was intended OR reference to a lock in which the combination can be changed through the use of a special key or tool without disassembling the lock.

Key Coding Machine: A key machine designed for the production of code keys. It may or may not also serve as a duplicating machine.

Key Control: Any method or procedure which limits unauthorized acquisition of a key and/or controls distribution of authorized keys OR a systematic organization of keys and key records.

Key Cut Profile: The shape of a key cut, including the cut angle and the cut root shape.

Key Cut(s): The portion of the key blade that remains after being cut and which aligns the tumbler(s).

Key Duplicating Machine: A key machine designed to make copies from a pattern key.

Key Gauge: A usually flat device with a cutaway portion indexed with a given set of depth or spacing specifications; used to help determine the combination of a key.

Key Interchange: An undesirable condition, usually in a master key system, whereby a key unintentionally operates a cylinder or lock. (See also Cross Keying, Controlled Cross Keying and Uncontrolled Cross Keying)

Key Locking Dial Ring: A dial ring containing a key lock to lock the dial and prevent rotation. Key Locking Dial: A dial ring that can be locked with a key to prevent rotation.

Key Machine: Any machine designed to cut keys. (See also Key Coding Machine and Key Duplicating Machine)

Key Manipulation: Manipulation of an incorrect key in order to operate a lock or cylinder.

Key Milling: The grooves machined into the length of the key blade to allow its entry into the keyway.

Key Override: A provision allowing for interruption or circumvention of the normal operation of a combinated lock or electrical device OR pertaining to such a provision, as in “Key Override Cylinder”.

Key Override Cylinder: A lock cylinder installed in a device to provide a key override function.

Key Retaining: Term used to describe a lock that will not allow its key to be removed while it is unlocked

eg. “Key Retaining Padlock”

Key Section: The exact cross-sectional configuration of a key blade as viewed from the bow toward the tip.

Keyor Keying Schedule: See Hardware Schedule

Key Symbol: A designation used for a key combination in the standard key coding system. e.g. A, AA, AA1, etc.

Key-in-Knob Cylinder: A cylinder used in a key-in-knob lockset. Also called a “KIK cylinder”.

Key-in-Knob Lockset: Any lockset with a key-operated cylinder in one or more knobs. Key-in-Lever Lockset: Any lockset with a key-operated cylinder in one or more lever handles.

Keyed Alike: Of, or pertaining to, two or more locks or cylinders that have, or are about to have, the same combination. They may, or may not, be part of a keying system.

Keyed Different: Of, or pertaining to, a group of locks or cylinders, each is, or is to be, combinated differently from the others. They may, or may not be, part of a keying system.

Keying Schedule: A detailed specification of the keying system, listing how all cylinders are to be keyed and the quantities, markings, and shipping instructions of all keys and/or cylinders to be provided.

Keyway: The opening in a lock or cylinder shaped to accept key bit or blade of a proper configuration OR the exact cross-sectional configuration of a keyway as viewed from the front; not always the same as the key section.

Kick Plate: A metallic plate used to protect the bottom of a door.

LFIC: Large Format Interchangeable Core.

Latch: A spring actuated bolt, normally with one or more beveled surfaces, that, when aligned with the strike, engages it automatically. (See also Deadlatch)

Lazy Pawl: A cam on automotive cylinders that does no turn until either the key operation or the interior locking devise rotates enough to contact the driver on the cam.

Leading Door Edge: The edge of the door opposite the hinges.

Leaf: One half or section of a hinge OR one door in a set of double doors OR one section of a multiple section door.

LOBC: (abbr.) Locked On By Combination; identifies a feature of some combination locks whereby the lock’s back cover cannot be removed unless the correct combination has been dialled – usually to a separate changing index.

Locking Mechanism: The part that stops access; can include the latch and/or the bolt. MACS: (abbr.) Maximum adjacent cut specification

Magnetic Rotating Device (MRD): A security device imbedded in the ignition lock of GM vehicles that uses Hall’s magnetic effect to detect when the ignition lock is broken and can then de-activate the ignition system of a vehicle.

Maison Key System: (from French, meaning “house” key system) A keying system where one or more cylinders are operated by every key (or relatively large numbers of different keys) in the system; eg. main entrances of apartment buildings operated by all individual suite keys of the building.

Manipulation-proof Lock: A combination lock designed to prevent identification of the combination without physical attack.

Master Keyed: Of or pertaining to a cylinder or group of cylinders that are, or are to be, combinated so all can be operated by their own change key(s) and by additional key(s) known as master key(s).

Master Pin: Usually a cylindrical-shaped tumbler, flat on both ends, placed between the top and bottom pin to create an additional shear line.

Master Ring: A tube-shaped sleeve located between the plug and shell of certain cylinders to create a second shear line. The plug is grooved around the body and the working key has corresponding notches cut into the bottom of the blade, allowing the key to turn in the cylinder.

Master Wafer: A special disc or wafer tumbler used in master keying, with dual or multiple key contact surfaces operating in conjunction with key blanks that have blades on opposite sides.

Maximum Adjacent Cut Specification: The maximum allowable difference between adjacent cut depths on a key.

Milling: The grooves cut into a key blank, along its blade.

Milling Cutter: A type of cutter used on a key machine that removes metal very rapidly from a key blank or a type of cutter used in a key blank factory, to produce the grooves in the sides of a key blank. Mogul Cylinder: A pin tumbler cylinder with a diameter of 2.0″, whose pins, springs, key, etc. may also be proportionally increased in size; frequently used in prison locks.

Mortise: An opening made to receive a lock or other such hardware OR the act of making such an opening.

Mortise Cylinder: A pin or disc tumbler cylinder made to operate a mortise lock. Mortise cylinders are normally screwed into the lock after it has been installed on the door.

Mortise Lock: A lock designed to install into a large mortise cut-out in the edge of a door. MP Lock: (abbr.) Manipulation-proof lock

Mullion: A fixed or removable vertical member dividing a door opening; may also occur between a door & side lite or a separate glazed area.

Multi-section Key Blank: A key section that enters more than one, but not all, keyways in a multiplex key system.

Multiplex Key System: A series of different key sections that may be used to expand a master key system by repeating bittings on additional key sections. The keys of one key section will not enter the keyways of another key section. This type of system always includes another key section that will enter more than one, or all, of the keyways OR a keying system that utilizes such keyways and key sections.

Mushroom Pin: A type of pin, resembling a mushroom, used in pin tumbler cylinders; used to add pick resistance to the cylinder. (See also Spool Pin)

Negative Locking: Locking that’s achieved solely by spring pressure or gravity that prevents a key cut too deeply from operating a lock or cylinder.

Night Depository: A safe containing a heavy-duty secured drop bin & envelope drop in a wall-mounted exterior depository for customers to make bank deposits.

Night Latch: A surface-mounted lock with a spring latch type of bolt.

Non-Fail Safe: See Fail Secure

Non-original Key Blank: Any key blank other than the original one.

Nose Puller: A tool for removal of the nose of a lever tumbler lock, allowing access to the tumblers.

OBD2: (abbr.) On board diagnosis; a data link connector that is required to be within 2 feet of the steering wheel.

OEM: (abbr.) Original equipment manufacturer

On Board Programming (OBP): Allows a user to program the vehicle to accept a new key, or fob without special tools.

One Column Progression: A process where key bittings are originated by using the cut possibilities in one column of the key bitting array.

One-way Cylinder: A lock cylinder been modified so that a key will only turn in one direction, eg. clockwise or counter-clockwise. Typically, an alternate key will operate in both directions.

Open-back Strike: A strike with an unenclosed opening opposite the lip edge. The open-back strike facilitates closing of the inactive leaf when the active leaf is already closed.

Opening Index: The reference mark on a combination lock’s dial ring used in dialling the combination to effect an opening. (See also Changing Index)

Operating Key: Any key that will properly operate a lock or cylinder to lock or unlock the lock mechanism and is not a control key or reset key. (See also Change Key)

Originate a Key: To cut a key to the combination of a lock where no key exists.

Padlock: A detachable and portable lock with a hinged or sliding shackle or bolt; normally used with a hasp and staple, or eye system.

Padlock Eyes: A pair of flat or angled metal brackets, always used in pairs; designed for a padlock shackle to go through both pieces.

Page Master Key: The level three master key for all combinations listed on a page in the standard progression format.

Panic Exit Device: A door locking device designed to grant exit by pressing on a cross bar that releases the locking bolt or latch.

Para centric: a keyway with one or more wards on each side projecting beyond the vertical center line of the keyway to hinder picking OR of, or pertaining to, a key blank made to enter such a keyway.

Parallel Arm: Term describes one of several mounting configurations for a surface-mounted door closer. In a “parallel arm mount” the arm of the closer is parallel to the surface of the door when the door is closed.

Passage Set: A device that includes a pair of door knobs and a spring latch, with no provision for any means of locking either knob.

Passive Entry Proximity Systems: (abbr. PEPS) An access control for vehicles; uses a higher power RFID that allow users to have the vehicle unlocked & started by simply being close enough to the vehicle with your proximity key or fob on your person.

Pattern Key: Any original key kept to use in a duplicating machine when additional keys are required OR any key used in a key duplicating machine to create a duplicate key.

Pawl: The cam attached to the end of certain automotive lock cylinders; driven by the plug and acts upon the latch mechanism to operate it. The pawl may or may not be attached to a linkage rod.

Peanut Cylinder: A miniature mortise cylinder. A peanut cylinder is 3/4″ in diameter, whereas a mortise cylinder is 1 5/32″ in diameter. (See also Mogul Cylinder)

PED: (abbr.) Panic exit device

Pick Gun: A tool designed to pick open locks by striking the bottom surfaces of the tumblers with a metal blade; usually shaped somewhat like a gun, with a trigger that causes the metal blade (pick needle) to strike the lock tumblers. There are mechanical and electric pick guns.

Pin Stack: All of the tumblers in a pin chamber, including top, bottom, and any master pins.

Pin Stack Height: The measurement of a pin stack, often expressed in units of the lock manufacturer’s increment or as an actual dimension.

Pippin File: A type of file used extensively when making of keys by hand. The pippin file gets its name from the shape of its cross-section, that of a tear-drop or of the seed of a pippin apple.

Pivot: A hinge with a fixed pin and knuckle, forming a single joint.
Plug: The part of a cylinder containing the keyway, with tumbler chambers usually corresponding to those in the cylinder shell.

Plug Bore: The hole in the cylinder where the plug fits into.

Pocket Door: A type of door that opens by sliding into a hollow wall.

Positional Master Keying: A method of master keying certain binary type disc tumbler key-in-knob locks, and magnetic and dimple key cylinders. Of all possible tumbler positions within a cylinder, only a limited number contain active tumblers. The locations of these active tumblers are rotated among all possible positions to generate key changes. Higher level keys must have more cuts or magnets than lower level keys.

Positive Locking: A condition brought about when a key cut that’s too high forces its tumbler into the locking position. This type of locking does not rely on gravity or spring pressure.

Practical Key Changes: The total number of usable different combinations available for a specific cylinder or lock mechanism.

Pre-cut Key: An unused key, usually a factory key, stocked for use when rekeying locks.

Prep Key: (abbr. for “Preparatory Key”): A key that must be used in conjunction with a renter’s key to unlock a safe deposit lock; usually the same for every lock within the installation. The term “Guard Key” is typically used in reference to double-nose SD locks, while the term “Prep Key” identifies a key having the same function on single-nose SD locks. (See also Renter’s Key and Guard Key)

Primary Key: In automotive lock terminology, the “primary key” is the key that operates the ignition lock. (See also Secondary Key)

Privacy Set: A device that includes a pair of door knobs and a spring latch, with a provision for locking the outside knob, and unlocking with the use of a simple tool rather than a key.

Profile Cylinder: A type of pin tumbler cylinder used extensively in Europe; fits entirely through the door and mortise lock and is secured by a single screw in the mortise lock’s face. The inside can be keyed or have a knob.

Progress: To select possible key bittings from the key bitting array, usually in numerical order. Progression: The logical sequence of selecting possible key bittings, usually in numerical order from the key bitting array.

Progression List: A bitting list of change keys and master keys arranged in the sequence of progression.

Pullman Latch: A curved, pivoting type of latch; used in many panic exit device designs and some unit lock and mortise lock designs.

Push Plate: A protective plate mounted on the “push” side of a door to limit wear of the door’s finish.

Rabbeted Door: A door having an edge contoured with an offset creating two surfaces which form an overlap at the abutting edge.

Rabbeted Lock: A lock with a face or front specially formed to use in a rabbeted door.

Rail: The horizontal construction member located on the top and bottom of a door. (See also Stile)

Rake: A certain type of lock-picking tool (noun) OR to pick a lock using a “raking” action (verb).

Random Master Keying: An undesirable process of creating a master key system utilizing unrelated keys.

Rap: To open a pin tumbler cylinder by applying a rapping action to the outside with a small wood or plastic hammer while applying turning pressure.

Re-locking Device: Any device intended to prevent normal opening of a safe as a result of an attack, two types are typically used, internal and external.

Recombinate: To change the combination of a lock, cylinder or key.

Record Safe: See “Fire Safe”

Rekey: To change the existing combination of a cylinder or lock.

Removable Cylinder: A cylinder that can be removed from a locking device by a key and/or tool. Removable Dial: A dial that’s removable from the spindle.

Renter’s Key: One of two keys required to open a safe deposit box. The renter’s key is the one issued to the box renter; it is unique key within the system. (See also Prep Key and Guard Key)

Request-to-Exit: (abbr. REX) A mechanism for a person to indicate to an alarm and/or electronic access control system, of their intent to exit through a protected door, preventing a forced door alarm.

Rim Cylinder: A cylinder typically used with surface-applied locks and attached with a back plate and machine screws; with a tailpiece to actuate the lock mechanism.

RKE: (abbr.) Remote keyless entry

Reveal: The distance measured from the trim surface of the jamb to the leading face of the door on the stop side when closed.

Roller Bolt: In detention lock terminology a “roller bolt” is the auxiliary latch bolt of a latch lock, due to the fact that it is often fitted with a roller on its end OR in safe lock terminology a “roller bolt” is a type of lock bolt that pivots to release, rather than sliding.

Root Depth: See Cut Root Depth
Rotary File: A type of key machine cutting wheel with a set of very fine teeth; removes metal somewhat slowly from a key blank. Also known as a “File Cutter”.

Rotating Constant: One or more cuts in a key of any level that remain constant throughout all levels and are identical to the top master key cuts in their corresponding positions. The positions where the top master key cuts are held constant may be moved, but always in a logical sequence.

Rotating Constant Method: A method used to progress key bittings in a master key system, wherein at least one cut in each key is identical to the corresponding cut in the top master key. The identical cut(s) is/are moved to different locations in a logical sequence until each possible planned position has been used.

Row Master Key: The level one master key for all combinations listed on the same line across the page in the standard progression format.

Safe: A lockable container for protecting its contents from fire and/or theft.

Safe Deposit Box: A dual custody container for the storage of valuables; rented to end users by a bank, trust company or hotel.

Safety Lock-out: A procedure to deactivate or render inoperative any energy device to ensure safety and give visual warning of danger while device is being worked on /locked out.

Safety Lock-out Hasp: A device used in conjunction with padlocks which allows multiple padlocks to be used to safely lock-out an energy device; often used on electrical switch panels and steam or hydraulic valves.

SAVTA: (abbr.) Safe and Vault Technicians’ Association

Scalp: The armoured face plate of a mortise lock or a thin piece of metal, usually crimped or spun onto

the front of a cylinder; determines the cylinder’s finish and may also serve as the plug retainer.

Screw-in Cylinder: Sometimes used to identify a mortise cylinder.

Second Generation Duplicate: Any key reproduced from the original.

Secondary Key: In automotive lock terminology, the secondary key is the key that opens door and compartment locks that the primary key does not.

Selective Master Key: An unassociated master key that can be made to operate any specific lock(s) in the entire system, in addition to the regular master key(s) and/or change key(s) for the cylinder, without creating interchange.

Sequence of Progression: The order in which bitting positions are progressed to obtain change key combinations.

Seven Column Progression: A process wherein key bittings are originated by using the cut possibilities in seven columns of the key bitting array.

Sex Bolt: Convex or flat-headed mating fastener used for through-bolting; consists of a female (internally) threaded barrel (nut) and a male (externally) threaded screw. The nut may have a knurled barrel to allow for one-sided installation; commonly used on door closers or exit hardware.

Shackle: The part of a padlock that passes through an opening in an object or fits around an object and is ultimately locked into the case.

Shear Line: A location in a cylinder at which specific tumbler surfaces must be aligned, removing obstruction(s) which prevent the plug from turning.

Shear Lock: A special-application electromagnetic lock (EML) designed to resist a shearing force (e.g. sliding the armature plate off the face of the EML rather than pulling straight away from it). Ordinary EMLs have little resistance to shearing force.

Shear-head Bolt: A security fastener commonly used in automotive applications; designed so that its head breaks off when the bolt is torqued, rendering it non-removable.

Shell: The part of the cylinder surrounding the plug; usually contains tumbler chambers corresponding to those in the plug.

Shim: Any small piece of material used to fit between objects in order to position one or both of them OR a small, flat piece of extremely thin metal with a crown to match the radius of a lock cylinder plug. A shim is used to open a pin tumbler cylinder by inserting it into the small space between the plug and the shell and using it to separate the top and bottom pins.

Shoulder: Portion of a key blank that normally forms the stop.

Shoulder Guide: Part of a key duplicating machine that facilitates proper positioning of the sample key and the key blank for duplicating.

Sidebar: A primary or secondary locking device in a cylinder. When locked it extends along the plug beyond its circumference. It must enter gates in the tumblers in order to clear the shell and allow the plug to rotate.

Sidewinder Key: A type of key with bittings milled into its side, rather than cut into its edge.

Silhouette Code: An illustration of a combinated key found in code books for use in originating keys.

Simplex Key Section: A single independent key section that cannot be used in a multiplex key system.

Single-acting: Refers to a door or door closer designed to swing in one direction only. (See also Double Acting)

Single-bitted Key: A key with cuts on only one side. (See also Double bitted Key)
Six Column Progression: A process wherein key bittings are originated by using the cut possibilities in six columns of the key bitting array.

Skeleton Key: A bit key with most of its material removed in order to bypass a variety of ward configurations: A sort of “master key” for bit key locks.

Slide Hammer: A heavy steel weight that slides along a shaft and strikes a stop at the end of the shaft. Slide hammers provide an impact in a direction away from the work, rather than toward it. It is a component of some pullers.

Slotter: A cutter designed to cut flat steel keys, ward lock keys and bit keys.

SFIC: Small Format Interchangeable Core

SMK: (abbr.) Sub-master key

Spacing: The dimension from the stop to the first cut and/or to the centers of successive cuts. Spindle: A threaded rod connecting the dial and the drive cam.

Spline Key: A small part that fits snuggly into a hole formed by grooves in two mating parts, securing them together. Spline keys are commonly-used in combination locks, to secure the dial spindle to the drive cam.

Split Pin Master Keying: A method of master keying a pin tumbler cylinder by installing master pins into one or more pin chambers.

Spool Pin: Similar in function to the mushroom pin, the spool pin gets its name from the fact that it is somewhat spool-shaped and is used to increase pick resistance. (See also Mushroom Pin)

Stacking: In master keying terminology, the term “stacking pins” refers to the practise of placing more than one master pin in a pin chamber; generally regarded as undesirable.

Standard Key Coding System: An industry standard and uniform method of designating all keys and/or cylinders in a master key system. The designation automatically indicates the exact function and keying level of each key and/or cylinder in the system, usually without further explanation.

Standard Progression Format: A systematic method of listing and relating all change key combinations to all master key combinations in a master key system. The list is divided into segments known as blocks, horizontal groups, vertical groups, rows, and pages, for levels of control.

Staple: The loop-shaped part of a hasp designed to receive the shackle of a padlock. (See also Hasp) Stile: Vertical members of a door to which the lock and hinges are applied.

Stop: The part of a key from which all cuts are indexed and which determines how far the key enters the keyway OR the part of a door or window frame against which the door or window closes.

Strike/Strike Plate: A metal plate installed onto or in a door jamb, header or floor, with one or more openings into which a lock’s latch and/or bolt can enter to lock the door.

Sub-assembled: When purchasing locks from a wholesaler, it is sometimes possible to purchase them without tumblers, springs, etc. This is often done with locks that will usually be keyed to the customer’s key at time of sale. Locks in this condition are normally called “sub-assembled” or “uncoded”.

Sub-master Key: The master key level immediately below the master key in a system of six or more levels of keying.

Tailpiece: An actuator attached to the rear of a cylinder.

Tension Wrench: A tool used in lock picking to apply turning pressure to the cylinder plug.

Theoretical Key Changes: The total possible number of different combinations available for a specific lock cylinder or lock mechanism.

Threaded Cylinder: A mortise cylinder

Three Column Progression: A process wherein key bittings are originated by using the cut possibilities in three columns of the key bitting array.

Throat Cut: A cut on some keys, usually flat steel keys for lever locks, that enables the key to turn and serves to hold the key in proper position as its turning.

Tibbe: A high security automotive lock system using rotating disc tumblers and their own key type. Time Delay Lock: A key or combination lock that incorporates one or two clock movements to impose a delay in unlocking. The delay period is typically between 3 and 30 minutes.

Time Lock: Used on safes and vaults, it is a lock with electronic or mechanical clock movements that remain locked for the number of hours that the operator has set. It is inaccessible from outside the container and typically has at least 2 clock movements. Locking times can be up to 144 hours or more, depending on the model.

Toe (of a Shackle): The end of the shackle on a padlock; may be removed from the case.

Tolerance: The deviation allowed from a given dimension.

Top Master Key: The highest level master key in a master key system.

Top Pin: Usually a cylindrical shaped tumbler, flat on both ends and installed directly under the spring in the pin stack.

Total Position Progression: A process used to obtain key bittings in a master key system wherein bittings of change keys differ from those of the top master key in all bitting positions.

Trunnion: A post and cam assembly having a slot the full length of its construction. A part of a lever lock which holds the key in place, and sometimes drives the locking bolt.

Try-out Keys: A set of keys of varying combinations, that is intended to encompass all possible combinations for a particular key/lock mechanism. Try-out keys often utilize modified, or custom, bitting depths in order to reduce the total number of keys necessary in the set, by exploiting the key/lock mechanism’s tolerance.

Tubular Key: A key with a tubular blade. The key cuts are made into the end of the blade, around its circumference.

Tubular Key Cylinder: A cylinder with tumblers arranged in a circle; operated by a tubular key; also knowns as a “radial pin tumbler cylinder”.

Tubular Lockset: A bored lockset with latch or bolt locking mechanism contained in the component installed into the edge bore.

Tumbler: A movable obstruction of varying sizes and configurations in a lock or cylinder that makes direct contact with the key or another tumbler and prevents an incorrect key or torque device from activating the lock or other mechanism. Examples include pins, discs, wheels, levers, etc.

Tumbler Spring: Any spring that acts directly on a tumbler. Turn Wrench: See Tension Wrench

Two Column Progression: A process wherein key bittings are originated by using the cut possibilities in two columns of the key bitting array.

Two Step Progression: A progression using a two-increment difference between bittings of a given position.

UL: (abbr.) Underwriter’s Laboratories

ULC: (abbr.) Underwriter’s Laboratories of Canada

Unassociated Change Key: A change key which is not related directly to a particular master key through the use of certain constant cuts.

Unassociated Master Key: A master key that does not have change keys related to it through the use of constant cuts.

Uncoded: Of, or pertaining to, a cylinder that is, or is to be, supplied without keys, tumblers, or springs. (See also Sub-assembled)

Uncombinated: Of, or pertaining to, a cylinder that is, or is to be, supplied without keys, tumblers, or springs. (See also Sub-assembled)

Uncontrolled Cross Keying: A condition in which two or more different keys under different higher level keys operate one cylinder by design; e.g. XAA1 operated by AB, AB1.

NOTE: This condition severely limits the security of the cylinder and the maximum expansion of the system, and often leads to key interchange. (See also “Controlled Cross Keying” and “Key Interchange”)

Underwriter’s Laboratories: A chartered not-for-profit organization to establish, maintain, and operate laboratories for the examination and testing of devices, systems and materials to determine their relation to hazards to life and property, and to ascertain, define and publish standards, classifications

and specifications for materials, devices, products, equipment, constructions, methods, and systems affecting such hazards.

Underwriter’s Laboratories of Canada: A not-for-profit independent product safety testing, certification and inspection organization founded in 1920. It maintains and operates laboratories and a certification service for the examination, testing and classification of devices, constructions, materials and systems to determine their relation to life, fire and property hazards.

Unit Lock: A lock be installed in a cut-out in the door edge without any disassembly or assembly required to the lock.

Universal Keyway: A lock with “universal keyway” is designed to accept any or all or a number of different key millings; has been associated with General Motors aftermarket locks.

Vertical Bolt: A type of bolt that travels up and down instead of from side to side, when the lock is operated.

Vertical Bolt Rim Dead Lock: A type of rim dead lock that uses a vertical bolt. Also known as a “jimmy proof lock”.

Vertical Group Master Key: The level two master key for all combinations listed in all blocks in a column in a page of the standard progression format.

Vertical Rod: Pertaining to a panic exit device that features locking points at the top and bottom of the door. Vertical rods connect the top and bottom latches to the center case of the panic exit device.

Wafer Tumbler: See Disc Tumbler

Wall Safe: A safe designed to be installed in a wall.

Ward: A usually stationary obstruction inside a key/lock mechanism that prevents turning of the key, unless the key has a corresponding ward cut.

Ward Cut: A modification of a key allowing it to bypass a ward.

Warded Key: A key with ward cuts only; typically a bit key, flat steel key or corrugated key.

Warded Lock: A key/lock mechanism that functions on the principle of wards and ward cuts.

Wheel Pack: A complete set of tumbler wheels, spacing washers, tension washers, etc. for a combination lock.

Wheel Post: Component of most combination locks on which the wheel pack is mounted.

Zero Bitted: Of, or pertaining to, a cylinder that is, or is to be, pinned to keys cut to the manufacturer’s reference number “0” bitting.