Abstract: A locking apparatus intended to be anchored in the bore of an element and to receive rotatably by snap-in closure a mating element provided with an undercut head. The locking apparatus according to the invention includes a substantially cylindrical body having first and second ends. Outwardly directed gripping means are arranged in the peripheral surface of the body at its first end. The body has a coaxially arranged cavity which narrows toward an opening in the first end. The cavity extends to the second end of the body and the body is provided there with an inwardly directed flange. The body is expansible or flexible at the first end.