Flange nut

This serves to distribute the pressure of the nut over the part being secured, reducing the chance of damage to the part and making it less likely to loosen as a result of an uneven fastening surface.

These nuts are mostly hexagonal in shape and are made up of hardened steel and often coated with zinc.

Flange nuts (and bolts) are widely used in automobiles and electronic products.

A flange nut is used inside a specially shaped dished-out washer.

If this nut were not used the object would have to be spot faced so as to provide a surface perpendicular to the fastener.