1. There is no national standard bolt called special bolt, which is generally used in special occasions and special purposes. The difference with ordinary bolts is whether there is a national standard.
2. Bolt: mechanical part, cylindrical threaded fastener with nut. A type of fastener consisting of head and screw (cylinder with external thread), which needs to be matched with nut for fastening and connecting two parts with through hole. This kind of connection is called bolt connection. If the nut is unscrewed from the bolt, the two parts can be separated, so the bolt connection belongs to the detachable connection.