one piece, self-locking fastener made of spring steel. The perimeter of the nut is rectangular in shape. Some variations have an arched base and/or corners which are trimmed or turned. Applications/Advantages - It reduces inventories by eliminating need for lockwashers and spanners. Its single thread engagement design makes it easy to apply and remove. Parts are reusable. Provides the correct amount of spring tension without damaging enamel, glass or porcelain surfaces.