The combination screw is a kind of screw, the screw is called industrial rice. Industry can't leave little screws. However, the combination screw is composed of a screw and a pincushion. Fasteners that are combined together by threads. The combination screw is easy to use, do not hand-match bolt, cushion, flat mat. So it's more convenient. But the price is a little bit more than the single bolt, the cushion, the pad add up.