Plain Washers are also known as Flat washers and their work is to distribute the fastener's load while reducing heat and friction during the tightening process. They can also be used as spacers, as is common in industrial and domestic applications. Plain washers do not have a locking function, rather they are used to protect the mating surface from damage. Plain washers can also be used when the hole is bigger than the nut. The main role of flat washers is to increase the size of a screw's bearing surface area and reduce the surface pressure applied on the fastened object. The most common type of washers is plain washers, also known as flat washers. Looseness can result when the bearing surface sinks under the surface pressure, so using a flat washer to reduce the surface pressure is very effective.