1. Bolts without national standards are called special-shaped bolts. They are generally used in special occasions and special purposes. The difference from ordinary bolts is whether there is a national standard.
2. Bolts: mechanical parts, cylindrical threaded fasteners equipped with nuts. A type of fastener consisting of a head and a screw (cylinder with external threads). It needs to be matched with a nut and is used to fasten and connect two parts with through holes. This type of connection is called a bolt connection. If the nut is unscrewed from the bolt, the two parts can be separated, so the bolt connection is a detachable connection.