The BB82 half Mortise 4-1/2” Door Hinge is a specialty hinge. The hinge fastens to the standard mortise slot on the door and the other leaf mounts on the face of the door frame. These are five knuckle, two bearing with square edges. They are constructed of 10 gauge (.134”) steel that is then plated to the desired finish. We ship in boxes of 3 hinges with the wood and machine screw.