Fasteners (byoura) are a general term for mechanical component parts such as screws, bolts, nuts, and rivets, used for fastening and securing other parts. Their primary role is to firmly join multiple components, providing an indispensable function for product assembly and structural maintenance. They are widely used in all manufacturing industries, including automobiles, aircraft, home appliances, buildings, and industrial machinery. The predominant manufacturing method is cold forging (header processing), which plastically deforms the material to form the fastener, thereby achieving high productivity and strength. Other important processes include thread rolling for forming screw threads, cutting for improving dimensional accuracy, and heat treatment and surface treatment (plating) for enhancing strength and corrosion resistance. Through these processing technologies, high-quality fasteners are produced to meet diverse environments and requirements.