To face the body is the creation of space, after determining the morphology and thickness of the surface front unit body, a plurality of unit surface assembled to the uniform space.

Thin wooden slats circle the unit to provide a smooth running surface to roll it and openings on the side and slated Windows let light into the interior.

And the way it will work is that you have to choose an orientation of a surface, which just means choosing one of the two possible unit normal vectors.