To facilitate direct replacement of a double sides function panel from the side direction by making a protruded edge part and a recessed surface part of the double sides function panel respectively contact with one side of a support and a side edge part of a dummy panel and connecting both of them to each other by a bolt in a state to sandwich both sides of the support by making the recessed surface part contact with an inside surface of the dummy panel after installing the dummy panel on the support.

A protruded edge part 10 and a recessed surface part 11 are formed on a double sides function panel 6, and a dummy panel 7 is formed of a hollow structured plate body. Thereafter, the protruded edge part 10 and the recessed surface part 11 are respectively made contact with one side of a support 2 and a side edge part of the dummy panel 7 after installing the dummy panel 7 on the support 2 by a bolt 12, and both of them are connected to each other by a bolt 14 in a state of sandwiching both sides of the support 2 by making the recessed surface part 11 contact with an inside surface of the dummy panel 7. Replacement of the double sides function panel 6 is carried out by removing the bolt 14. Consequently, it is possible to easily and directly replace the double sides function panel from the side direction.