Spacecraft . square pyramid jig Posted on December 1, 2015December 5, 2015 by dkoa 4 pcs 1in angle bar chamfer cut and welded to form square inverted pyramid with sturdy base, metal off-cuts. square pyramids made with 4 pcs. iron rod with single weld bead at tip should be self-supporting. pre-cut all iron rods to identical length using metal cutter, saw or angle grinder. 16 pyramids required to fabricate one semi-octet truss.