The spring-loaded piece of metal that retracts when you turn the handle. It usually has a curved edge so the door can "click" shut without you turning the knob.

[Key inserted] | v +-----+-----+ | | | <-- Housing (Bible) | o | o | | | | | | <-- Driver pins (spring-loaded) | | | | | | ---+--- | <-- Shear line (critical gap) | | | | | | o | o | <-- Key pins (touch the key) | | | +-----+-----+ | | | | KEY | <-- Key bitting (hills/valleys) +-----------+ | [Turn to unlock]

An electric strike replaces the standard strike plate on the door frame.

The diagram visualizes "ghost shear lines."