Glossary of locksmithing terms

Lock Components
– Bible: Contains pins and pin stack springs
– Bit: Section of the key that enters the lock and engages the bolt or tumblers
– Bitting: Physical arrangement of the key’s bit that engages with the locking mechanism
– Blade: Segment of a key that enters the keyway of a lock and has key cuts machined into it
– Bolt stump: Rectangular part in lever tumbler locks that passes through the slot in the levers as the bolt moves

Key-related Terms
– Bottom pin: In a pin tumbler lock, the pin in contact with the key
– Break: Separation in the pins used to encode the lock for a specific key or set of keys
– Key cut: Depression in a key that allows it to turn in its lock
– Key pin: Another term for bottom pin
– Master pin: Optional pin placed between top and bottom pins to allow different keys to open the lock

Lock Mechanics
– Lock housing: Part of the lock that does not move and transfers the action of the key to the bolt
– Plug: Part of a cylinder lock that turns when a key is inserted
– Shear line: Point where the inner and outer cylinder meet in a cylinder lock
– Snib: Device to engage or disengage a lock without a key
– Strike plate: Metal plate on the doorjamb with a hole for the bolt to hold the door closed

Security Features
– False gate: Mechanical element in lever or disc tumbler locks to make picking more difficult
Glass relocking device: Glass attached to spring-loaded bolts to prevent burglary attacks
– Security pin: Non-standard pin designed to make lock picking more difficult
– Spool pin: Security pin shaped like a cable reel
– Thermal relocking device: Equipped with a fusible link to release the relocking device if the temperature exceeds a certain threshold

– Apex Security: What is a lock bible?
– Keith Mayers: A Dictionary of Locksmithing (PDF)
– Mick Friend: The Encyclopaedia for Locksmiths
– NerdWallet: What is a safe deposit box?
– Historical Locks: Lock housing with boltSources: