Template:POTD/2013-10-23

The pin tumbler lock is a lock mechanism that uses pins of varying lengths to prevent the lock from opening without the correct key.

Without a key in the lock, the driver pins (blue) are pushed downwards, preventing the plug (yellow) from rotating.
When an incorrect key is inserted into the lock, the key pins (red) and driver pins do not align with the shear line; therefore, it does not allow the plug to rotate.
When the correct key is inserted, the gaps between the key pins and driver pins align with the edge of the plug.
With the gaps between the pins aligned with the shear line, the plug can rotate freely.

Diagram: Wapcaplet and Pbroks13