Polyhedra lovers are fond of certain compound shapes, such as this symmetric arrangement of five concentric regular tetrahedra. If you like to make things in wood, it’s a natural challenge to cut some plywood, bevel the edges, and screw or glue together a giant geometric model. Here is Dale Seymour with his compound of five tetrahedra.


One of the five is made of four large triangles and serves as an inner support to which the facets for the other four tetrahedra were added. Below you can see the facets before assembly.


In a similar style, Dale made this colorful compound of five concentric cubes.


See all of George Hart’s Math Monday columns

Gareth Branwyn

Gareth Branwyn

Gareth Branwyn is a freelance writer and the former Editorial Director of Maker Media. He is the author or editor of over a dozen books on technology, DIY, and geek culture. He is currently a contributor to Boing Boing, Wink Books, and Wink Fun. And he has a new best-of writing collection and “lazy person’s memoir,” called Borg Like Me.