PURPOSE: To surely regulate positions with a less number of position controlling pieces to be mounted to steel plate blocks by improving said pieces in assembling a blast furnace, a storage tank or the like.

CONSTITUTION: Restraining pieces 11, 13 are welded in a shop to the same height as the side edge of each block. The pieces 11, 13 are formed of steel plates of an L shape, and are welded 11a, 13a at one end thereof respectively to blocks 2, 2a. The other end sides 12, 14 thereof are aligned respectively to the end faces of the blocks. In addition, grooves are formed. In assembling these, the pieces 11, 13 are joined each other and 12, 14 are welded. Hence, the site welding of the restraining pieces entails welding the pieces to themselves and this permits simple and sure welding.