Tom Hull's Five Intersecting Tetrahedra

Tom Hull's Five Intersecting Tetrahedra (FIT) is a modular origami model that requires 30 individually folded units, each assembled from a separate sheet of paper. The units interlock without glue or tape to form the final geometric structure of five interpenetrating tetrahedra.

Tom Hull designed the Five Intersecting Tetrahedra in 1995, and it has since become one of the most iconic and frequently folded modular origami models in both mathematics and origami communities. Hull, a mathematics professor, created the model to explore the intersection of geometry and paper folding.

The model represents the compound of five tetrahedra, a geometric figure related to the symmetry group of the icosahedron and dodecahedron. Each tetrahedron is inscribed within the same sphere, and their edges intersect to create a striking three-dimensional pattern that visually demonstrates principles of polyhedral compounds.

Most folders use rectangular paper, often cut from squares into approximately 1:2 aspect ratio rectangles, for the 30 units. Using paper in five different colors—six units per color—helps highlight the five individual tetrahedra in the final assembled model.