Support and hanger system fasteners are a kind of mechanical parts used for fastening and connection and are widely used. All kinds of fasteners can be seen on all kinds of machinery, equipment, vehicles, ships, railways, bridges, buildings, structures, tools, instruments, meters and supplies. It is characterized by a wide variety of specifications, different performance and uses, and the species degree of standardization, serialization and generalization is also very high. Therefore, some people also call a class of fasteners with existing national standards as standard fasteners, or standard parts for short. Fasteners are the most widely used mechanical basic parts. With China's entry into WTO in 2001, it has entered the ranks of international trade powers. China's fastener products are exported to countries all over the world, and fastener products from countries all over the world are also pouring into the Chinese market. As one of the products with large import and export volume in China, the realization of fasteners in line with international standards has important practical and strategic significance for promoting Chinese fastener enterprises to go to the world and promoting fastener enterprises to fully participate in international cooperation and competition. Due to the specification, dimension, tolerance, weight, performance, surface condition, marking method, acceptance inspection, marking and packaging of each specific fastener product..