Abstract: Fastening device for fixing a screw or the like in a hole or opening in plaster board, or the like. It comprises a sleeve with a flange placed at one side of the board and a nut fixable against the back of the plaster board. A mounting screw is passed through the sleeve and the nut. The sleeve has an inner cone and the nut has a corresponding cone which extends into the inner cone. As the nut and sleeve are drawn together, the cones engage and spread the sleeve. The sleeve is provided with at least one pair of slits defining longitudinal tongues which are spread. A screw inserted through the sleeve into the nut pulls the cones together. The nut itself is provided with wings which may be bent out against the back surface of the board. The tightening of the nut on the screw thereby results in anchoring the nut against the back surface of the board and pulls the flange of the sleeve against the front surface and spreads the slit sleeve.