Which type of nuts are designed to accept a cotter pin or lock wire for safetying?

Castle nuts are specifically designed to accept a cotter pin or lock wire for safetying, which is essential in applications where secure fastening is critical. The unique design of castle nuts features notches on the top that allow for the insertion of a cotter pin, which helps prevent the nut from loosening due to vibration or movement over time. Using a cotter pin or lock wire effectively secures the nut in place, providing an added level of safety, especially in high-stress applications such as in aviation and mechanical systems.

This feature is particularly important in maintaining mechanical integrity in systems where failure could lead to significant safety hazards. In contrast, other types of nuts do not have this built-in capability for safetying, making castle nuts the preferred choice for situations that require a robust fastening solution.