A sleeve nut(barrel nut) is a type of fastener that has internal threading and is used primarily in furniture making. It’s also known as an insert nut or threaded insert nut because it can be inserted into pre-drilled holes for a secure fit. The most common types of sleeve nuts are made from steel, stainless steel, aluminium, brass, and plastic. They come in various sizes, shapes, and thread counts, so they can be used for different purposes.

A sex bolt is a type of mating fastener (nut) that has a barrel-shaped flange and protruding boss that is internally threaded. The bolts sits within the components being fastened, the flange provides the bearing surface. The sex bolt and accompanying machine screw sit flush on either side of the surfaces being fastened.