Pin tumbler lock

A cylinder lock in which spring-loaded pin stacks of varying lengths block rotation until a correctly cut key aligns their pins at the shear line.

Shear line: The boundary between a lock’s plug and housing, across which pins must align for the plug to rotate. The key lifts each pin stack until its gaps meet at this boundary.
Lock cylinder: A replaceable or integral housing containing a key-operated plug and its locking components. The pin stacks sit in its chambers above the plug.
Egyptian lock: An ancient wooden pin lock in which a large key lifted pins to release a bolt. It is an early precedent for using pins lifted by a key.
Wafer tumbler lock: A lock that uses flat spring-loaded wafers, rather than stacked cylindrical pins, to control plug rotation. It uses a related shear-line principle with flatter tumblers.
Door lock: A device fitted to a door to restrict or permit its opening. Pin tumbler cylinders are commonly used to operate door locking hardware.
Key bitting: The pattern of cuts or depths on a key that corresponds to a lock’s pin arrangement. Its cut depths determine how far each key pin rises.
Keyway: The shaped opening in a lock plug through which a key is inserted. Its profile guides compatible keys into position beneath the pin stacks.
Linus Yale Jr.: An American inventor whose compact cylinder lock helped establish the modern pin tumbler design. His work adapted pin-based locking into a practical cylinder mechanism.
Lever tumbler lock: A lock in which a key raises levers to align gates and release a bolt or plug. Its levers replace the pin stacks that govern this lock’s rotation.
Master key system: A lock arrangement in which change keys open individual locks while a master key opens multiple locks. Pin configurations can be designed to accept more than one key.

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