To enhance working efficiency for fitting into a hollow slab pipe and prevent the fitting part from becoming damaged.

A large-diameter part 5 and a small-diameter part 6 are formed on a pipe using a stepped part 4 as a border, and a a coil member 3 is set in place outside the small-diameter part 6, and further the base end part of the coil member 3 is firmly fixed to the large-diameter part 5. Next the coil member 3 is squeezed into a drain hole bored in the lower part of the peripheral wall of the hollow slab pipe from the tip side. Consequently the peripheral wall of the hollow slab pipe is nipped into an interval between the coiled tubes of the coil member 3 and at the same time, the small-diameter part 6 is inserted into the drain hole part. Further, the stepped part 4 is fixed in such a state that it is brought into contact with the outer face of the peripheral wall of the hollow slab pipe. Thus it is possible to avoid damage during conveyance by performing an installation work on the site.