Jargon buster

Let's be honest, there's quite a lot of jargon used in the security world so we thought you'd appreciate a guide which provides you with information on a lot of the terms used & referred to by security specialists.

This guide just explains the terms so if you need some decent security advice then speak to us for more information.


Anti-thrust bolt

A spring bolt, for a night latch particularly, which cannot be pushed back when it has shot out and fastened a door, although it can be withdrawn by knob or key. This security device is usually achieved by a dog inside the latch case which falls behind the bolt and keeps it shot out when an auxiliary slide is pushed in.

Anti-thrust plate

An overlapping metal plate fitted to outward opening doors so as to prevent access to lock bolts.

Automatic deadlatch

A deadlatch, the main bolt of which is automatically locked (or deadlocked) when the door is closed.


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


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”.

Barrel Bolt

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

Birmingham Bar

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

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.


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.

Bow (of key)

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