PURPOSE: To prevent the side slipping of a base plate, by overlappingly constituting, rotatably in right and left, two large and small disklike upper and lower washers having through holes, in which the lower surfaces are protrudedly formed and which are decentered from a center, in the washers for a steel frame, etc.

CONSTITUTION: The lower side washer 1 having a large diameter and a roundness state, and the upper side washer 5 having a small diameter, are formed, and protruded parts 2 and 6 are provided respectively on the lower surface of both the washers 1 and 5. An anchor bolt 10 is drilleingly mounted in through holes 3 and 7 for putting into, while decentered from a center. The through hole 3 of the lower side washer 1 is made to fit to the outer diameter part 6a of the protruded part 6 of the upper side washer 5, and the through hole 7 of the upper side washer 5 is made to coincide with the diameter of the anchor bolt 10. In this constitution, the protruded part 6 of the upper side washer 5 is engaged with the through hole 3 of the lower side washer 1 to be overlapped by both the washers 5 and 1, the protruded part 2 of the lower side washer 1 is engaged with the hole 12 of a base plate 11 to be mounted, and the anchor bolt 10 is put into the through hole 7 to be engaged by a plain washer 15 and a nut 14.