PURPOSE: To make a backing plate installing work to be a safe work on a floor by forming a backing plate main body for closing gap around a pipe of resilient matter which is easily deformed, and forming the resilient matter in a spiral form of a large curvature.

CONSTITUTION: A resilient backing plate main body 1 of a spiral form is of sponge-like resilient matter of foaming urethane or the like. The form of the main body 1 is formed taking a vertical line 5 for the axis of a vertical section 2 and taking a height 5 for a step of a spiral for spiral rotation. The width of a belt-like spiral surface 6 is equal to a width 3 of the vertical section, and the length is proportional to the number of spiral rotations of the main body 1. The spiral of the main body is opened to make the surface 6 circular to close gap around a pipe, and change of a surface in the form of the gap is coped with the width 3 and the length.