To simplify time and labor-requiring tile-pasting work and form an sloped mounting walking surface with ease and at low cost, and eliminate the need for skilled work simultaneously, and provide an uniform finishing effect.

This unit comprises a combination of a thin-walled mounting plate (a) and a thick-walled mounting plate (b) where the top of the thin-walled plate (a) and the thick-walled plate (b) form an inclined surface 19 slanted substantially with an angle α of inclination. The wall thickness of the maximum thickness area 3 on the inclined upper end of the thin-walled mounting plate (a) is substantially identical to that of the minimum wall thickness area 4 on the inclined lower end of the thick-walled mounting plate (b).