Abstract: A substantially rigid, segmented, flat sheet blank parallelogram, which, may be shaped and folded into a reversible three dimensional rectangular parallelepiped. The sheet includes six foldably connected side wall panels, each in the form of a parallelogram, preferably a square or rectangle. The sheet also includes additional material such as support panels, and/or border material which defines, with the six side wall panels, the sheet blank in the shape of a parallelogram of the present invention. In preferred embodiments the flat sheet blank parallelogram is rectangular in shape. In some embodiments there is no excess border material, while in still other preferred embodiments there are no support panels.