PURPOSE: To cope with any positional drift of an attaching hole caused by the extension contraction due to temperature change, etc., when flat board parts of work members are joined to each other by a bolt or the like so that the attaching hole may be conformed in the range wider than conventional one.

CONSTITUTION: Attaching holes 2, 4 in their form including rectangles are respectively bored in flat board parts 1, 3 of work members to be joined together. The flat board parts 1, 3 are overlapped with each other, and the attaching holes 2, 4 are crossed to each other. A bolt 5 is inserted through the common hole part, and then the work members are joined by tight fastening by nut 6 or the like.