PURPOSE: To adjust the inclination to the ground of a starting block and the width between right and left blocks by enabling the angle of rails to the starting block to be adjusted, and enabling the starting block to be shifted in parallel to the rails.

CONSTITUTION: When an inner side plate 36 is rotated in the direction of an arrow A around a pivot pin 37, a foothold 38 also rotates, in the direction of the arrow A, and the tilt angle changes. When it rotates completely, a side plate 36 separates from a side plate 34, and a hand can be brought close freely to the inside of the side plates 36 and 34. An angle adjusting rod 42 which is provided by being energized with a spring to the upper part of the downside of the foothold 38 is set at an optional angle by being locked to an optional hook 36a. Moreover, each of starting blocks 10, 10 is shifted along the rail 12, and is locked in an optional cut 16, and is fixed to a coupling including an auxiliary coupling 30, with a bolt and a nut.