what do washers do for screws

Washers are used with screws, bolts, and nuts to distribute the load of the threaded fastener and prevent damage to the joint's bearing surface. They also prevent movement, corrosion, and loosening of the fastener over time. Washers can protect surfaces from marring, indentation, and friction, and can be used as spacers or to absorb vibrations. They can also prevent galvanic corrosion and increase the tightness of the joint. The thickness and type of washer used depends on the specific application. Not all materials require the use of washers, but they are useful for soft materials like wood.