Nylon nuts also called screw grommets are designed to attach side marker lights and various trim panels. They usually fit into a square hole and accept various screw sizes. This design allows the applicator to fasten the marker light or panel securely without the nut spinning in the hole. It also acts as a gasket for water leakage. 

Nylon nuts are a must have for their unique locking mechanism. They contain a nylon insert that encloses the threads during installation, providing extra reinforcement against vibrations. Grommets are also essential for many applications.