Self-tapping screws are used for connecting thin metal plate (steel, saws, etc.) between. When connected to the first connector member is made out of a tap drill hole, and then self-tapping screws into the threaded bottom outlet is connected member. Since the self-tapping screw thread surface with high hardness (≥HRC45), you can attack a threaded bottom outlet is connected to the internally threaded member, thereby forming a connection.