PURPOSE: To make it possible to carry out its fastening work only from one side, by providing an anchor rail in an anchor base which is semi-elliptically cut out at opposite sides of one portion about the end of its shaft, and making it that two anchors connected together by means of an anchor pin move on this anchor rail and are fixed to the end of the anchor.

CONSTITUTION: An anchor base 5 is formed within a shaft 6 which is semi- elliptically cut out at opposite sides of one portion near its end, and two anchors 4 connected together by means of an anchor pin 3 which moves on an anchor rail 1 formed within the anchor base are mounted to the base. In order to fasten the shaft 6 and the anchors 4 together, they are lined up when the pin is inserted into the hole of each of the assemblies. When the pin has made to pass through the hole of each of the assemblies, each of the anchors 4 naturally rotates by 90° and further moves on the anchor rail 1 and is then fixed to the anchor end 2. The assemblies are then fastened to each other by a washer 7 and a knut 8 from the side at which the top of the pin is located. Thus its fastening work is achieved only from one side; moreover, the anchor end 2 having screw threads, it can also be used as a bolt as in conventional ways.