Bolts refer to a type of fastener without a head, featuring threads on both ends. During assembly, one end must be threaded into a part with an internal threaded hole, while the other end passes through a part with a through hole. The nut is then tightened to securely connect the two parts into a single unit. This type of connection is known as a bolt connection and is a removable type. It is mainly used in situations where one of the connected parts is relatively thick, requires a compact structure, or where frequent disassembly is not suitable for bolt connections.