A strong 3D structure like the arm of a construction crane or stage lighting rig.
InstructionsMake a 2-D truss section by tracing the pattern. The pattern repeats every four inches. Extend the truss to the desired length by moving down four inches and adding more sections. Make four pieces of equal length. In the following steps, they are combined to make a box-like 3-D truss. Lay one piece flat. Hold a second one at right angles to it, with their long sides touching. Add plastic to weld them together along their length. Make sure the two pieces are lined up evenly and are at a right angle. The structure is stronger if the joints are aligned correctly. Combine the second and third pieces the same way as in step 4. Now you should have two long right-angle beams. Put one beam on the table and line up the other one on top of it so they form a long, square box. Weld the two seams along their length.