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.

Action - The arrangements of live or latch bolts and their accessories in a lock or latch, and how they function.

Alike change - More than one lock or latch which can be operated by the same key.

All to pass - Often referred to as “locks to pass” i.e. a numb of locks which can be passed or keyed alike (opened by the same key).

Angle cuts - A measurement usually expressed in degrees, for the angle between the two sides of a key cut.

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a night latch particularly, which cannot be pushed back when it has shot out and fastened a door, although it can be withdrawn by knob or key.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.

Armoured forend - The American term for a double forend, comprising one inner and one separate outer forend.

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

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