Key retaining locks

A key retaining lock is a lock design in which the key cannot be removed from the lock without the lock beind returned to the locked state. This is most often used on padlocks to require that the shackle be closed before the key can be removed.

In key-retaining padlocks, the movement of the plug and cam to release the shackle forces in ball bearings that hold the cam in place until the shackle is returned to the locked position.