To enable an extruded shape which decorates an edge section of a top board material to be easily attached to the top board material so that the corrective adjustment and the corrective replacement can be executed easily.

A groove 12 is formed on an upper surface of the edge section 13 of the top board material 1 along the edge section 13. The extruded shape 2 includes a longitudinal portion 20 to cover the end face 14 in the edge section 13, an upper lateral portion 21 to extend to the back from an upper section of the longitudinal portion 20, an insertion portion 22 into the groove 12 to project downward from the upper lateral portion 21 and a lower lateral portion 23 to extend to the back from a lower section of the longitudinal portion 20. A pitch x between the insertion portion 22 and an upper surface 23a of the lower lateral portion 23 is made to be approximately equal to the thickness of the top board material 1 or more and a tightening shaft 25 is disposed in the lower lateral portion 23 of the extruded shape 2 to be fixed by screwing in a female screw hole 23b formed in the lower lateral portion 23 and to be vertically movable by screwing.