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Difference between Master Key and Bump Key

Difference between Master Key and Bump Key

A bump key is a special key that is cut to the deepest level for all the teeth in the key. It is designed to be put into the lock and then hit with a solid object to make the tumblers in the cylinder bounce until they are in alignment with the shear line. The shear line is a gap that when the tumblers are aligned allows to cylinder to turn and the bolt to be withdrawn so the lock opens.

A bump key can be used to open any lock that uses the same blank key which means that the number of channels cut in the key, the length, the height and thickness are identical. Only the groves for the tumblers are different for each key. When the tumbler pins are not in alignment, the cylinder cannot turn.

Some locks are designed to use two keys. The first key is the individual key for that specific lock. The second key is a master key that can open that lock and all the other locks in a group that are designed to use that specific master key. This is done by adding another pin. The normal key may raise the tumblers to align with the shear line at the top of the third pin. The master may move the tumblers so the shear line is at the bottom of the third pin.

There is also a wafer that varies in length that allows the master key open all the locks in the group. In other words, each lock is individually adjusted so that the master key can open it. Master keyed locks are designed for apartment complexes, classroom doors in schools or office doors in businesses so that only one key is needed by employees to get into the rooms.  Bump keys are used when no other key is available to gain entry and master keys are used routinely to prevent employees from having to carry dozens of keys so they can do their jobs.