PURPOSE: To install an extrusion-molded hollow board to a structure frame in the stabilized state.

CONSTITUTION: Bolt holes 13 are drilled at the center in the breadthwise direction on the upper and the lower parts of an extrusion-molded hollow board 10, and zigzagged metal plates 14 are attached to the board with connecting bolts 15 that are inserted through the bolt holes 13. The zigzagged metal plates 14 are welded to guide angles 18 that are fixed to structure frame beams 17, and the extrusion-molded hollow board 10 is attached to the guide angles 18 at the center on the upper and the lower parts. Both ends on the upper and the lower parts of the extrusion-molded hollow board 10 are held to the guide angles 18 with support metal fixtures 20 that are inserted into hollow through holes 10a of the extrusion-molded hollow board 10.