| 摘要 |
PROBLEM TO BE SOLVED: To avoid the accumulation of foreign matters in water. SOLUTION: A main body 3 formed to a trench shape, and a projection 18 located below the opening end surface 11 of the trench of the main body 3 are provided; a plurality of projections 18 are formed in the inner peripheral direction 13 which intersects with the trench direction 7 of the main body and are provided with intervals in the trench direction 7 of the main body, and they are formed in such a manner that a lid portion 24 covering the opening 9 of the trench of the main body 3 can be placed on the top end 20 of the projection.
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