Washers serve as essential accessories in bolted joints, improving fastening performance and durability. Flat washers distribute load evenly and prevent damage to surfaces. Spring washers add tension to resist loosening from vibrations. Lock washers have features such as teeth or splits to prevent nut rotation. Other specialized washers like fender washers provide larger surface areas, while shoulder washers insulate and guide fasteners. Materials and finishes vary to protect against corrosion, electrical conductivity, or mechanical wear, making washers adaptable across virtually all industries.