The following Glossary of Locksmith Terminology is provided courtesy of the Master Locksmith Association (MLA). Click on a letter below to be taken to its corresponding terms.

Backplate -The plate, fixed on a door, to which the moving parts of a lock or latch are attached.

Backset - The horizontal distance from the outside face of the outer forend to the centre of the keyhole or follower hole (or both). Designated as the “keyhole backset” or “follower backset”.

Banbury Lock or wooden stock lock - An old style door lock in which the various metal pieces are fitted separately in a block of wood which, in effect, forms the lock case.

Bar (of Lever) - The part between the pockets which is slotted to allow the bolt stump to pass through.

Barrel - See "Plug".

Barrel and Curtain - This is the full name of a security device fitted in some locks to turn and close the keyhole when the key or any other instrument inserted through the keyhole is turned. The barrel is a tubular part surrounding that portion of the shank of the key which enters the lock, and the curtain, attached to the barrel, is a disc fitting close to the underside of the cap of the lock. A spring with its end to enter the notch in the edge of the curtain is usually fitted to keep the barrel and curtain in place.



Barrel Bolt - The common kind of door bolt having a round shoot running in a long continuous guide or strap attached to the backplate, the shoot being provided with a knob or the equivalent for operation by hand.



Barrel Key - An American term for pipe key.

Bathroom lock - A lock with a springbolt operable on both sides by furniture, and a deadbolt operable from the inside only, usually by thumb turn.

Belly (of Lever) - The edge, generally curved, which the key touches.

Birmingham Bar - A steel bar fitted to the inside face of a door frame on the hinge side.

Bit (of key) or key bit - That part of a key which is specially shaped or notched to operate the mechanism of its own particular lock or latch.

Bitting - The shaping or notching of a key blank to transform it into a key to operate its own lock or latch. Blade (of key) That part of a cylinder or lever key that is to be or has been notched.

Blank (key) or key blank - A partly made key, which has been shaped to enter the keyhole of a certain type of lock or latch, but of which the blade has not been finally notched to operate any individual lock.

Bolt - The part of a lock or latch which provides the fastening or engagement by protruding from the case or forend to engage in the staple, striking plate, link, shackle or other member.

Bolt head - The portion of a bolt that protrudes beyond the case or forend of a lock.

Bolt hole - The hole in a case, forend, plate or staple to guide and/or admit the bolt.

Bolt Stump - According to some authorities, this is the name of the part that upstands, usually rectangular in section, on a dead bolt or runner which passes through the slot or gating in the levers as the bolt moves.



Bow (of key) - That part of the key which is held in the fingers when operating the lock or latch.

Box Lock - A lock for fitting to the front of a box with a hinged lid. In the larger sizes the bolt of the lock, usually key operated, has two locking points to engage the two links on the linkplate which is fixed to the lid.



Box Striker or box striking plate - A striking plate having a box shape around the bolt hole to receive the deadbolt, used for greater security.



Bridge Ward - The kind fitted in some two side locks, the wards being fixed to a plate or bridge which is in the centre of the thickness of the lock and carried on cheeks.



BSS British Standard Specification - Authorised and issued by the British Standards Institute, the accepted UK authority for all standards of performance, tests and manufacture.

BS 3621:200:2004 - British Standard specification for Thief Resistant Locks for hinged doors. Locks submitted for certification must satisfy the requirements of the ten stringent clauses of the specification

Bullet or Bulleted - 1. In a key, bullets are the longitudinal grooves or projections or both on a key bit requiring a keyhole formed to suit,
2. In a lock, they are the corresponding grooves or projections or both at the keyhole, designed to prevent the entry of a key which is not properly shaped.



Burglar Bars - Steel bars, usually round or square in profile, frames. cut to length and fixed internally to window

Bush - A lining (usually brass) around the key - or follower - hole in a lock case, giving smoother working and longer life to the rotating parts. The keyhole bush is often milled so as to form wards on one or both sides of the inside of the lock case. See "Sashwards".

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