The local museum is putting together a diorama of the Juno Beach D-Day landing and I was volunteered to build the beach obstacles. the Czech hedgehogs were fairly easy to build from plastic angle but the tetrahedrons were not cooperating :? . That is until I switched to paper modeling! A bit of time on the computer figuring out a graphics package (Visio), some more work designing the part, some grey paper from the local craft store and voila, tetrahedron tank obstaces.