Archi-forms, die-cut printed cardboard and plastic hinges. Contributed by Studio Infinity.
[20 F, 54 E, 36 V] This shape is also a compound of two decagonal prisms, but there are two pairs of decagons (ten-sided polygons) that are each in the same plane. So each pair of decagons fuses into a non-convex octadecagon (18-sided shape), making this an octadecagonal prism. It illustrates the Archi-forms construction system created by Marke Levene of Lemniscate, Inc., sold in the 1990s by Y & B Associates. The construction system is unique in consisting of separate regular polygonal faces together with pressure-fit 360-degree hinges with which to link them into polyhedral forms. Hence any convex or non-convex polyhedron with regular polygonal sides could in principle be constructed from Archi-forms.