In an effort to complete a Periodic Table of Polyhedra
in origami, I began to by producing the lower polyhedra. There are two unique pentahedra. One is a pyramid with a square base, and the other is the triangular prism. The one shown here is a "regular" triangular prism, having all edges of unit lengths and faces of regular polygons, and only a single type of vertex. I not sure why is it not considered an Archimedean solid; I guess because it bears no particular relationship to any Pythagorean solid.