Working just like a pop rivet or rivet gun, a rivet nut turns a drilled out hole into a captive nut perfect when the surface in question is too thin to be tapped, or access to the rear is impossible. A rivet nut can be applied to an existing hole if it is a suitable size, or a new hole can be drilled to suit your desired rivet nut and bolt. Once you have determined the size, the rivet nut tool must be equipped with the appropriate mandrel.