(1) The upper pin in a pin tumbler lock. This pin obstructs the shear line when no key is inserted into the keyway. A driver is usually chamfered or flat on both ends. There are some locking systems which use varying length drivers to compensate for the different length bottom pins. (2) Metal part used to mount the cylinder bar onto the rear of a Schlage pin tumbler cylinder. The driver and clinder bar are secured onto the rear of the plug using a c ylinder cap. Drivers vary depending upon lock type and application. Also known as Top Pin