Design your truss. These instructions will produce a truss approximately 10 inches wide. Avoid trusses more than 12 feet in length unless you have the assistance of a professional structural engineer to manage longer spans.
Select three or four equal lengths of 2 inch diameter steel pipe, depending on the design. Separate them into two groups of two pipes for a square truss, or one pair of pipes and a third pipe for a triangular truss.
Fabricate connectors for both ends of the truss. Use lengths of rectangular-shaped steel channel, 1 ½ inches in width, by ¾ inches in thickness, by 2 ½ inches in length. Weld three pieces together in the center so they form a three "armed" star shape for a triangular truss, or four pieces to make a four "armed" X shape for a square truss. Use reinforcing plates to join these pieces, top and bottom. Make two connectors for each truss. Each "arm" must be the same length. The final connector should measure 5 inches in width from end to end. All connectors must be identical.
Weld a connector between two pipes, placing the connector about ½ inch in from the end of the pipe. Weld the connector to all remaining pipes. Repeat at the opposite end of the pipes. All the pipes should be rigidly connected at both ends, and should form a perfect triangle or square when this stage is completed.
Measure and mark 12 inches on center along the length of all the pipes. Start the marking from the end of the first pipe but stagger the marks by 12 inches on the corresponding pipe above the first pipe. Count the number of marks on one pipe and take this number times three. This will produce the number of cross support rods you will need.
Fabricate 3/8 inch diameter steel rods to form cross supports in the quantity needed. Cut the rods 12 inches in length. Use a rod shear or cold saw to cut the rods.
Weld one end of rod on one pipe. Extend the rod, on the diagonal, up to the staggered mark on the pipe above the first pipe. Weld the rod to the second pipe on this mark. This will create a diagonal connection between the two pipes.
Weld another rod on the second pipe, at a diagonal, but leading down to the pipe below to the next mark. The two rods will form a triangular shape.
Weld rods between pairs of pipes as well, for a four-sided unit. Continue welding cross support rods in this fashion until the entire truss is "filled" with triangular-patterned cross supports.
Drill holes through the pipes for attaching rigging hardware like eye bolts.