To prevent the infiltration of rain from a hanging hole by a method wherein a cushioning material is installed onto the underside of a plate mounted so as to close the top face of the handing hole and water stops tightly set up onto the internal surface of the hanging hole and a slipping-off preventive material are laminated successively to the lower section of the cushioning material and fixed integrally to the plate.

A cushioning material 12 is fitted onto the underside of a plate 11 installed so as to close the top face of the hanging hole of a covering plate, tapered water stops 13, which are inserted into the hanging hole and mounted on the internal surface of the cushioning material 12 in a watertight manner and in which an outside diameter is reduced gradually towards the front end of a lower section, are stuck on the underside of the cushioning material 12, and a slipping-off preventive member 14 is caulked to the lower section of the water stops 13 through a shaft 15 droopingly provided onto the underside of the plate 11. Watertightness between the water stops 13 and the covering plate is ensured and rainwater does not infiltrate into the inside because the water stops 13 are set up onto the internal surface of the hanging hole in the watertight manner, and the infiltration of water from a clearance with the covering plate can be prevented because the cushioning material 12 made of a rubber is joined with the underside of the plate 11.