Abstract: A top wall for closing an upper opening of a rectangular frame is formed continuously with an upper edge of a side wall disposed on one side of a row consisting of four side walls. An upper flap having a supporting wall is folded to form one article supporting section on an upper edge of a side wall adjacent to the side wall. A lower flap to which a bonding portion continuous with the upper flap is fixed is formed continuously with the lower edge of the side wall. An upper flap is formed continuously with an upper edge of a side wall disposed on the other side of the row and has a shorter supporting wall. The upper flap is folded to form another article supporting section opposed to the one article supporting section. A lower flap is formed continuously with a lower edge of the side wall. A bonding portion continuous with the supporting wall is bonded to the lower flap. At least one supporting window is defined on each of upper supporting portions and each of the supporting walls.