I use this octahedral structure in a ton of stuff i'm building ,both mechanics and electronics. It can be built for next to nothing from trash, can scale up or down in size and extent and can be made fast with minimal skills.
Tools needed: duct tape, marker, 6 inch equilateral triangle, which I show how to make in another instructable, an optional nylon cord or piece of clothesline, and cardboard box scrap.
Step 1: Trace Out and Cut Out 6 Triangles
trace as shown, draw inner triangles by hand as shown with ruler, cut it all out with box cutters. Don't stab yourself.
Step 2: Lay Out Triangles, Duct Tape Them Together
Lay out all six triangles as shown in a line. Create joints using duct tape on both sides as shown. Fold up into a octahedron with both a open top and open bottom then seal the joint with some more duct tape or cut holes with the box cutter and wind the cord through it and tie a square knot for something you can easily open and re-close. Using various tie lines and rubber bands and more cardboard these can be easily stacked and connected with tetrahedra of the same size, making an extendable matrix of work spaces where machines can be built and modified.