Abstract: A lock has an outer housing, which has an outer slot at an interior side. An inner housing is received in the outer housing for rotation and has an inner slot and a driving section. Three locking plates are received in the inner housing, each of which has and a recesses at a periphery thereof. A movable pin is moved to be received either in the inner and outer slots or in the inner slot and the recesses. A first tumbler pin is provided at the outer housing and has an end received either in the annular slot or in the position slot. The inner housing is reciprocated between a first position, in which the position pin is moved to a position slot to restrain the inner housing from rotation, and a second position, in which the position pin is moved to an annular slot to release the inner housing.