A lock includes a body, a key-operated core in the body, two spring-biased plates slideable on a recessed portion of the body, and a locking crutch to be fastened to the body with the spring-biased plates. The body has crutch embedding holes on two sides of the core; the core has a plate part, and force is applied to the spring-biased plates through the plate part when the core is turned. The locking crutch has a groove on each of two ends to engage a corresponding plate. The plates are biased to engage the locking crutch when the core is in the locking position; and, the plates are forced to disengage from the locking crutch by turning the lock core to the unlocking position. Saw-resistant pins are inserted in receiving holes formed on a periphery of the lock body to protect the lock against a saw.