A flat washer is a thin, disk-shaped hardware component, typically made from metal, plastic, or rubber, designed to distribute the load of a fastener like a screw or bolt. It is placed between the fastener head and the surface it is being fastened to, reducing friction, preventing wear, and helping to ensure a secure fit. Flat washers also serve to prevent damage to the material being fastened and can act as spacers or provide insulation. They are commonly used in various applications, including construction, automotive, and machinery assembly, due to their versatility and effectiveness.