Abstract: A door lock has four separate locking bolts operated or controlled by a single key-operated tumbler lock. The key-operated lock is located directly above two conventional external doorknobs, in a conventional arrangement, so that a would-be thief is unaware of the fact that the door lock contains four locking bolts, rather than the two locking bolts that are conventionally used. The four locking bolts achieve a level of security that is not attainable with the conventional two locking bolt arrangement.