PURPOSE: To increase a holding effect so largely by spreading a coil-form holding member over the surface of a covering grounding, fixing it tight, and covering this holding member with a covering material.

CONSTITUTION: Each of stationary auxiliary members 6 provided with a hooded projection 8 is attached to a covering grounding 4 for a wall surface or ceiling or the like at proper intervals, while a metallic expansible coil 2 is set up in a direction orthogonal with the auxiliary member 6 and it is engaged with the hooked projection 8 and locked tight. Next, a covering material is spayed out of a nozzle 10 so as to cover the auxiliary member 6 and the coil 2 on the surface of the grounding 4, thereby forming a covering material layer 12. With this constitution, a desired stacking covering material holding characteristic is thus securable.