Abstract: A lock and key combination including a lock cylinder made by connecting a plurality of locking pieces in a stack, each locking piece including a base, which has a top recess at the top side, a front recess, keyway in the middle of the front recess, and a plurality of receiving chambers disposed in the front recess at two opposite sides by the keyway, a plurality of retainer elements mounted in the receiving chambers and forced by a respective spring toward the keyway and having a respective lug at one side, an actuating plate mounted within the front recess of the base, having a projecting locating plate at the top inserted into the top recess of the base and forced upwards by a spring, and a plurality of T-shaped control slots which receive the lugs of the retainer elements, and a cover fastened to the base by hooks and cover over the actuating plate, wherein when the lugs of the retainer elements are moved to the unlocking position by the key, the projecting locating plate is forced into the top recess of t