To make it possible to extremely easily position a work by mounting a bumper to a main body mounted at a stretch and swiveling the bumper by the angle of inclination of a work.

The main body 3 is slip coupled to the stretch 4 and an adjusting screw 5 is screwed to the main body 3. The adjusting screw 5 is loosened to move the main body 3 in a lateral direction along the stretch 4, by which the main body 3 is positioned in the lateral direction (X-axis direction). A supporting member 2 extending in a longitudinal direction (Y-axis direction) is fixed by means of a screw 12 to the main body 3 and a contact part 2A is fixed longitudinally to the supporting member 2. A nut 9 is slip coupled to a guide 11. The nut 9 is screwed to a ball screw 10. The bumper 1 is abutted against the work, by which the work is positioned. An angle reading plate 7 is fixed to the supporting member 2 and the angle corresponding to the angle of the inclined part of the work is stated thereon. The nut 9 is moved by rotation of the ball screw 10 and the bumper 1 is swiveled by means of a connecting rod 8.