PURPOSE: To prevent the occurrence of a slide drop accident and allow the repeated use of a lining board by fitting slide motion stoppers in superposed state to the slope surface of the lining board liable to slide.

CONSTITUTION: Engagement projections 1a are formed on the front and rear, and upper and lower sides of longitudinal battens 1 and 1, and coupled to holes i2 drilled through four corners of a lining board (i). Furthermore, the battens 1 and 1 are fitted in superposed state to the upper surface of the board (i) having an inclination angle of i2 at a rising gradient 8 for covering the upper surface of joists h' and so forth laid above the ground (a). In addition, a plurality of slide stopper projection rows 2 having approximately angular cross section are laid on the upper surface of three longitudinal battens 1 at the predetermined intervals for intersection in an arrow (a) direction.