a fastening
Fastener is a kind of mechanical parts used for fastening connection and widely used. Fasteners are widely used in various industries, including energy, electronics, electrical appliances, machinery, chemical industry, metallurgy, mold, hydraulic and other industries. All kinds of fasteners can be seen in various machinery, equipment, vehicles, ships, railways, bridges, buildings, structures, tools, instruments, chemicals, instruments and supplies. They 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 also refer to a class of fasteners with existing national standards as standard fasteners, or simply as standard fasteners.