Bolts are usually defined as a threaded fastener intended to be mated with a nut, while a screw can engage either preformed or self-made internal threads. Bolts and screws share a number of head shapes and drive configurations. Bolts which have a shank configuration preventing rotation cannot be considered -- or used -- as a screw. Conversely, fasteners with cutting or tapered threads not intended to mate with a nut, such as self-tapping screws, cannot be used as bolts. A stud is an externally threaded headless fastener. One end usually mates with a tapped component and the other with a standard nut.