Abstract: An expanding fastening element joins two structural members such as two pieces of girder of which one has a slot with lips at the sides thereof, so that the two members may be separated again when desired. The expanding fastening element includes two legs that are hinged together and may be opened out by way of a fixing screw into a locking or gripping position with hook-like heads of the legs hooked onto the lips. Before tightening the screw the fastening element is positioned at the desired position in a hole in one girder by a guide sleeve or plug locking into the second member and springingly pushed outwards from the fastening element by a spring within it.The two legs or gripping members have keeper heads and slots at their ends opposite to the hooked heads to take up a c-like ring spring.