| 摘要 |
PROBLEM TO BE SOLVED: To provide covers for closing drainage ditches formed on a floor surface, make it possible to adjust the height of the covers and enable the visual recognition of the state inside the drainage ditches. SOLUTION: Openings of drainage ditches 12 and 14 are closed with covers 20 and 34. Main bodies of the covers 20 and 34 are composed of transparent plates 24 and 36. Screw holes 28 and 40 and drain holes 30 and 42 are formed in the transparent plates 24 and 36. Bolts 26 and 38 are screwed into the screw holes 28 and 40 from the lower side of them. The lower ends of the bolts 26 and 38 touch down on the bottom faces of the drainage ditches 12 and 14. The heights of the transparent plates 24 and 36 can be adjusted according to the degree to which the bolts 26 and 38 are screwed into the holes.
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