| 摘要 |
PROBLEM TO BE SOLVED: To use the same inspection hole (an outer frame and an inner frame) in common even when materials housed in the inner frame differ from one another. SOLUTION: The inspection hole structure is composed of a rectangular outer frame 1 in plan view and a rectangular inner frame 3 in plan view set into the outer frame 1, a mortar housing section 15 is formed to one surface in the inner frame 3 and a plastic-tile housing section 16 is formed to the other surface, and the inspection hole structure is constituted so that the housing section 15 and the housing section 16 are inserted to the outer frame 3 under either of the state in which the mortar housing section 15 is directed upwards or the state in which the plastic-tile housing section 16 is directed upward, and has a locking means 25 of the outer frame 1 and the inner frame 3 capable of being used in both types of a mortar housing type and a plastic-tile housing type in combination.
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