| 摘要 |
PROBLEM TO BE SOLVED: To decrease the number of parts of a back board piece by forming a channel being recessed upward in the longitudinal direction of the back board piece on the end part being brought into contact with at least the side wall part of another back board in a facing straight line-shaped back board. SOLUTION: A back board member 1 is to prevent water from penetrating into an opening for inserting a bathtub in a bathtub part. In this case, the back board member 1 is divided into back board pieces 3 wherein a channel 4 being recessed upward over the whole length is formed on a square rod material with a rectangular crosssection. For example, it is divided into the first member 3a used in the longitudinal direction of a bathtub and the second member 3b used in the width direction. In the first member 3a, the side wall parts 12 on both sides of the back board 1 are formed by the outer wall faces of the side wall parts 12 on both sides of the channel 4 and both end parts thereof are formed into butting faces 5 as butting end parts 13a. On the other hand, in the second members 3b, one of the side wall parts 12 on both end parts 13 thereof is formed into a butting face 5 as a butting face part 12a. |
