To contrive to realize the fastening of a fitting by one touch, the insurance of the precision of the head part of the fitting and an automatic unfastening by means of the demolding of a sleeper by a method wherein this device is equipped with a spring-loaded ball internally fitting to a tubular member and a positioning shaft part introducible and extractible in and from a positioning hole at the lower part of an opening part so as to press the datum side surface of the head part of a fitting against the other side surface of the opening part along the longitudinal direction of a form.

By loosely engagingly connecting a fastening bolt 27 through an engaging part 27b to a rail fitting 1 and inserting the positioning shaft part 27a at the lower end of the bolt into the positioning hole 25 of an opening part 15, a planar positioning is executed. The large diametral part at the lower end of the inclined plane S at the intermediate part of the bolt pushes a ball 22 against a spring in a tubular member so as to pullingly energize the bolt downwards in order to abut the lower end of the head part against the top surface of the tubular member when the large diametral part passes through the ball 22. A spring steel 17 pushes a side surface S2 opposite to the datum side surface S1 of the head part against the other side surface (b) of the opening part 15 along the longitudinal direction of a form, resulting in ensuring the accuracy of the angle and position of the datum side surface S1. As a result, the fastening of the fitting 1 and the automatic unfastening by means of the demolding of a sleeper can be realized and the accuracy of the angle and position of the head part of the fitting can be ensured.