Washer (hardware)

A washer is a flat, typically disc-shaped piece of hardware made from various materials, such as metal, plastic, or rubber. It is used in conjunction with a fastener, like a bolt or screw, to distribute the load over a larger surface area and to provide a smooth bearing surface, preventing damage to the material being fastened. Washers also help prevent loosening due to vibration and can provide a seal to prevent the escape of liquids or gases.