Tukey, a young mathematics instructor. The models were named hexaflexagons—“hexa” for the six triangles that form the hexagonal face, and “flexagon” for the structure’s ability to flex.

When the cross-section is a triangle, the prism is called a triangular prism. When the cross-section is a hexagon, the prism is called a hexagonal prism. Image caption, The faces of a prism are ...