Excellent Quality: These nuts are made of high quality zinc plated carbon steel which provides strength and good corrosion resistance in many environments. Easy to use: These versatile threaded nuts allow you to use them easily, easy to use. Features: Insert nuts are advantageous over cylindrical nuts and T-nuts because they can be installed from one side of the workpiece. Matching Kit: There are 6 different sizes of nuts (please see size details in description or photos) so you can handle your project for free. Note : the pre-drilled hole should be as deep as the length of the insert nut plus any part of the bolt that can be screwed past the end of the nut into the work piece An insert nut provides a threaded socket for a wooden part, similar to an anchor wall. These insert nuts are inserted into a screw pre-drilled hole, in this case the external protrusions bite into the wood, preventing the nut from turning or pulling out.