PURPOSE: To prevent rain water from leaking from through-places where eye bolts, which are at the top of a building unit and through which the building unit is hung, are passed through, as much as possible, by tensioning elastic materials each having a slit at the through-places on the ceiling surface of a curing cover.

CONSTITUTION: A curing cover 10 is composed of a ceiling surface 11 and four sides 12, using tarpaulin. At the four corners of the ceiling surface 11 of the curing cover 10, through-places for eye bolts 21 each are formed, and the eye bolts 21 are provided at four corners of a building unit 20 for the purpose of hanging the building unit 20. Almost square elastic materials 13, 13 each are partially tensioned at these through- places. Slits, each of which has a round hole at the center thereof, are separately provided on the elastic materials 13, 13 and at the end parts of the slit, round-shaped punching treatment for preventing tearing-up is done. Furthermore, the diameter of the round hole is made much the same as the diameter of the shank of the eye bolt 21 or slightly larger than the diameter thereof, and the round hole is positioned at the place where the shank part under the head of the eye bolt 21 passing through the slit is held. In this way, the clearance between the round hole and the shank part of the eye bolt 21 is almost filled up.