Lock Glossary

back plate - metal strip used to fasten a cylinder to a door

backset - distance between the center of a cross-bore and the bolt edge of a door

barrel key - key with a bit projecting from a hollow cylindrical shaft

bible - part of the cylinder shell that houses the pin chambers

bitting - numbers that represent the cuts of the key

blade - portion of a key that contains the cuts

blank - uncut key

bolt - part of lock that moves into locked or unlocked positions

bottom pin - cylindrical tumbler that makes contact with the key (aka tumbler or key pin)

bow - part of the key used as a handle

bump key - key modified to open locks when bumped while being turned with slight pressure

bypassing - opening a lock in a non-standard way such as shimming or carding

cam - part of a lock which activates the bolt or latch

case - body or housing of a lock

chamber - cavity in a cylinder plug or shell that houses the tumblers

change key - key that operates only one group of keyed alike cylinders in a keying system

clevis - metal link for attaching a chain to a padlock

code key machine - device for cutting a key when its cut depth numbers and spacing are known

comb pick - tool used to lift all pin tumblers of a cylinder above their normal shear line

control key - key used to remove an interchangeable core

core - removable cylinder and plug used in a interchangeable core system

core key - key which is used to remove a core

cylinder - unit consisting of the plug shell, tumblers, springs, plug retainer, a cam/tailpiece and all other necessary operating parts

cuts - notches cut in the key to make it fit a lock

deadbolt - a lock with a bolt that resists end pressure once extended

double bitted key - key cut on both sides of the blade

driver spring - spring at top of the pin stack exerting pressure on the pin tumblers

effective plug diameter - key cut depth plus length of bottom pin required to reach shear line

flat key - key used for warded or lever tumbler locks that is flat on both sides

grand master key (GMK) - key that opens two or more groups of locks that are each operated by a different master key

great grand master key (GGMK) - key that opens two or more groups of locks that are each operated by a different grand master key (GMK)

key gauge - flat device with indexed slots for a given set of depth or spacing specifications used to help determine the combination of a key

key milling - grooves along the length of the key blade to fit the keyway

keyed alike (KA) - two or more locks having the same combination

keyway - opening in a lock shaped to accept key blade of a proper configuration

lever - flat, spring-loaded tumbler which pivots on a post

master key (MK) - key that opens all master keyed locks in a group, each lock having its own change key

master key system - keying arrangement having two or more levels of keying

master pin - cylindrical tumbler with flat ends placed between the top and bottom pin

maximum adjacent cut specification (MACS) - greatest allowable difference between adjacent pin sizes according to the lock manufacturer

mortise lock - type of lock with a case inside a mortised out pocket in the edge of the door

mushroom pin - top pin resembling a mushroom used to make locks harder to pick

pin stack - combination of a bottom pin, optional master pins and top pin

plug - part of the cylinder containing the keyway

plug follower - tool used to allow cylinder plug removal while retaining the top pins and springs

plug spinner - tool to rotate a picked cylinder plug quickly so it cannot lock while rotating

retainer pin - pin seated on a spring which keeps the retainer cap in place

rim lock - latch typically mounted on the surface of a door or drawer

shackle - curved part of padlock that fits around an object or into an opening

shear line - dividing line between the plug and the shell

shell - part of the cylinder surrounding the plug which contains tumbler chambers

shim - thin piece of metal used to open a lock without using a key

shoulder - part of the key that prevents it from entering the lock further

skeleton key - non-cylinder key with a blade cut away to allow it to bypass wards

slimjim - narrow strip of spring steel used to unlock vehicle doors

spool pin - pin in shape of a bobbin which acts as a deterrent to picking

top pin - cylindrical tumbler with flat ends installed directly under the spring in the pin stack (aka driver pin)

tumblers - pins in the lock which are moved to the shear line by the key

wafer - disc in a wafer lock that, once aligned by the key, can be turned in either direction to open the lock

ward - obstruction in a lock preventing in incorrect key from entry or turning