PURPOSE: To constrain displacement owing to a load in a horizontal direction exerted on a support leg even when the load is exerted thereon by a method wherein a fixing fitment is coupled between the support legs of a waterproof pan.

CONSTITUTION: A fixing fitment 1 is coupled between a pair of adjoining support legs 14 and 14. A bolt 2 is joined screwed in a state with one engaging part 1a of the fixing fitment 1 formed of a plate-form substance formed in such a manner that two ends are bent in a U-shape in cross section to form engaging parts 1a. The engaging part 1a has a given depth (x) enough for engagement with the support leg 14, and a distance (y) between the engaging parts 1a and 1a is set to a value slightly longer than a distance between a pair of support legs 14 and 14 to which the fixing fitment 1 is fixed. In fixing of the fixing fitment 1 to the support leg 14, the fixing fitment 1 is placed along a pair of the support legs 14 and 14. The engaging part 1a on the side where the bolt 2 is joined in a screwed-in state therewith is pulled. After the other engaging part 1a is engaged with the support leg 14, the bolt 2 is screwed in. The tip of the bolt is driven until it is brought into contact with the support leg 14, the bolt being fastened. The fixing fitment 1 is coupled between a pair of the support legs 14 for integral formation, and the fall in a horizontal direction of the support leg 14 is constrained by the fixing fitment 1.