Fasteners are a type of mechanical parts that are used for fastening connections and are extremely widely used. Fasteners are used in a wide range of industries, including energy, electronics, electrical appliances, machinery, chemicals, metallurgy, molds, hydraulics, etc., in various machinery, equipment, vehicles, ships, railways, bridges, buildings, structures, tools, and instruments All kinds of fasteners can be seen in, chemicals, instruments and supplies, etc., which are the most widely used mechanical basic parts. It is characterized by a wide variety of specifications, different performance and uses, and a high degree of standardization, serialization, and generalization. Therefore, some people call a type of fasteners that have national standards as standard fasteners, or simply standard parts.