rivet nut

A rivet nut, also known as a blind nut, rivnut, threaded insert or nut-sert, is a one-piece internally threaded and counterbored tubular rivet that can be anchored entirely from one side. There are two types: one is designed to form a bulge on the back side of the panel as a screw is tightened in its threads. The other is similarly drawn in using a screw, but is drawn into the sleeve instead of creating a bulge.