PURPOSE: To reduce the parts cost by using inexpensive pipes in stead of expensive hexagonal nuts used so far and reduce the processing cost by deforming plastically the pipes without cutting as in the case of the hexagonal nut and by calking a mounting board for a floor panel.

CONSTITUTION: A panel-mounting plate 10 is fixed to a pipe 9 by calking the panel-mounting plate 10 placing a floor panel with the pipe 9. On the other hand, a female screw 9b is provided at the inner periphery of the pipe 9 and a male screw 8b provided at the outer periphery of the post 8 is fitted in the female screw 9b.