If you need to buy locking nuts, then nylon insert nuts are a good bet. How do these nuts work, and what are the advantages of using them? What Are Nylon Insert Locking Nuts? Nylon insert locking nuts create a tight locked bond with their bolts or screws. They do this because they have a nylon or plastic part that sits at the top of their design. When you attach this kind of nut, the bolt or screw initially sticks when it meets the insert.