The Sonobe unit is a modular unit attributed to Mitsunobu Sonobe in the 1970's. It is one of the best known of all modular units, being both a convex and concave edge and face unit.

Folding the ModelEdit

Begin with a square.

  1. Fold and unfold.
  2. Fold to the creases.
  3. Fold to the center.
  4. Tuck inside.
  5. Crease. Note the fold in the center.

Assemble by inserting the triangular flaps into the triangular pokets near the center of another unit.


There are theoretically an infinite number of assemblies assuming an infinite number of piecesAssemblies include:

  • 1 unit: right triangle
  • 2 units: square
  • 3 units: triangular bipyramid/Toshie's jewel/hexahedron(non-regular)
  • 6 units: cube/tetrahedron/regular hexahedron, finned non-regular hexahedron
  • 12 units: octahedron, cube, finned cube/tetrahedron
  • 24 units: cube
  • 30 units: icosahedron

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