A cover-shaped nut, as the name suggests, is a hexagonal nut with a cover. The main function of the cover is to prevent the exposed part on the outside of the fastening from being covered, so as to prevent moisture or other corrosive substances from entering and thus play a role in rust prevention, thereby increasing the service life of the nut itself and the connecting parts.

Different sizes of studs require different sizes of cover nuts. For extra-long studs, taller cover nuts are used. There are also self-locking cover-shaped nuts, which have twisted threads in the hexagonal area to form a tight friction fit and prevent the nut from loosening due to vibration.