By rotating one part 12A, 12B to invert one part with respect to the other, the hinging features 14A, 14B of the two parts 12A, 12B can be interleaved with one other.The various mounting holes and other features required are provided at both the top and bottom of each part 12A, 12B to allow mounting of the flip down shelves 32A, 32B and prop rod 60 as described below in either vertical orientation