Plain washers, also known as flat washers, are integral components in the realm of fastening technology, serving a critical role in distributing the load of a threaded fastener, such as a bolt or screw, over a larger surface area. This dispersion of load not only helps in reducing the pressure on the material being fastened but also protects the surface from damage during the tightening process. Constructed from a variety of materials including steel, stainless steel, brass, and nylon, plain washers are selected based on their compatibility with the application's environmental conditions and the physical properties required. Their simplicity belies their importance in preventing stress concentration and in ensuring the structural integrity of assembled parts by providing a smooth, flat surface that reduces friction and prevents leakage, making them indispensable in both industrial and domestic applications.