Heptominoes are polyominoes made of seven connected squares. There are 108
distinct heptominoes including the red coloured one, which has a hole. In the
plane this piece cannot be made to fit with the other heptominoes. Using cubes
instead of squares you get solid heptominoes, the hole can be filled and you
need not discard this shape. With 108=2x2x3x3x3x7 heptominoes many rectangular solids, scale models and other symmetric configuration can be built. 

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