Abstract: A cylinder lock which comprises a housing and, rotatably accommodated therein, a cylinder having an axially extending key slot for reception of, and rotation by, a mating key to unlock the lock. The cylinder is provided on at least one of its ends with an end plate having a similar key slot cut therethrough and means for removably attaching the end plate to the cylinder with the key slot of the end plate in register with the key slot of the cylinder to permit insertion, through the end plate, into the cylinder, of the key, whereby in case of a broken key, the end plate can be removed from the cylinder, thereby exposing a portion of the broken key, facilitating extraction thereof.