What is the difference between special-shaped bolts and nuts and ordinary bolts and nuts

What is the difference between special-shaped bolts and nuts and ordinary bolts and nuts:

1. Bolts and nuts without national standards are called special-shaped bolts and nuts, which are generally used in special occasions and special purposes. The difference with ordinary bolts and nuts is whether there are national standards.

2. Bolts: mechanical parts, cylindrical threaded fasteners with nuts. A type of fastener consisting of a head and a screw (cylinder with external thread), which needs to be matched with a nut to fasten and connect two parts with through holes. This type of connection is called bolt connection. If the nut is unscrewed from the bolt, the two parts can be separated, so the bolt connection is a detachable connection.