Abstract: The cylinder lock assembly includes a cylindrical lock housing having an inner core extending between first and second ends. The inner core defines a core axis extending through the first and second ends. A lock cylinder is received in the inner core for rotational and axial movement in the inner core. The lock cylinder includes an axially extending key slot for receiving a key therein and a radially extending slot extending through the lock cylinder and intersecting the key slot. A rotation plate assembly is received in the radially extending slot and blocks at least a portion of the key slot. The rotation plate includes first and second rotation plate members which are movable relative to each other. A first biasing member engaging the first and second rotation plate members urges the second rotation plate member radially away from the first rotation plate member.