One of the main advantages of the modern cylinder lock is the fact that it is not necesary to alter the boltwork to change the cylinder. In fact, changing your average door lock requires the removal of exactly one screw, removal of the cylinder, going to the hardware store or the lock guy with the cylinder (best) or measurements of said cylinder (if you want to lock your door while you are absent) showing the length of cylinder and the distance right and left from the moveable pin part so you get the right replacement. Depending on the cylinder, it costs (where I live) between