PURPOSE: To improve safety of a lock by providing a barrel, rotatable within a cylinder and a plurality of rods, actuating using a key a tab provided at each rod, and thus forming a proper combination of forming parts so that the lock can be unlocked.

CONSTITUTION: A barrel rotatable within a cylinder 2 and a plurality of rods 3 are provided and a tab 5 is attached to each rod 3. The tabs 5 are actuated by means of a key to form a forming part in a selected position. When the use of the proper key allows the combination of the forming parts formed in the rods 3 to coincide with cylinder-forming parts arranged on the inner peripheral surface of the cylinder 2, the barrel becomes rotatable within the cylinder 2 and the lock is unlocked.