To provide a positioning tool which can minutely adjust the location and inclination of a recess forming material embedded in a foundation, for forming an anchor implanting hole, after being temporarily set in a form, and is applicable to various foundations different in dimension.

An anchor ruler A which is mounted on a foundation form F when the foundation B for supporting a base isolation device S of a single ball rolling bearing type is constructed, is formed of an octagonal plate 10 and form mounting portions 20 for hanging the plate 10 in the foundation form F in a height adjustable manner. The plate 10 can be inscribed on each of the two column forms different in dimension by rotating through 45 degrees, and the plate 10 is formed with mounting holes 13a, 13b for mounting a widing pipe P thereon as the recess forming material corresponding to the location of an anchor bolt Va of each of the two column forms different in dimension. Then, a hook fitting of the form mounting portion 20 has its upper end hooked on an upper bed of the foundation form F, and its lower end connected to the plate 10 by means of height adjusting bolts 24.