What does a castle nut look like?

A castle nut is a type of nut that is used to secure various fasteners in place. In the context of firearms, a castle nut is a small, round nut with multiple notches or castellations cut into its outer circumference. These castellations are designed to prevent the nut from rotating when properly secured with a cotter pin. The castellated design of the nut allows the cotter pin to be inserted through a hole drilled in the nut and the fastener shank, thereby locking the nut in place.