Saw two pieces of iron pipe and a rear cross-member to a width that works for your desk space, such as 4 feet. Saw two pieces of iron pipe and two side bracing pieces to your desired length, such as 3 feet. Lay the four pieces in a rectangular formation on a flat surface, such as the floor.
Use four three-way, 90-degree elbow-tube clamps to connect the four pipes into a rectangular shape. Tube clamps are suitable for designer furniture and easy to use, as they are fixed onto the tubes with an Allen key and grub screw rather than nuts and bolts. Tighten with the Allen key, ensuring that the unused orifices are all pointing upwards.
Saw four pieces of iron pipe to the length of the legs you wish your desk to have, such as 2-1/2 feet. Insert one end of each leg into one of the upward facing orifices on the three-way, 90-degree elbow-tube clamps. Tighten with the Allen key.
Place and loosely tighten a three-way, through-corner tube clamp halfway down one of the rear legs. Insert the cross-member into the appropriate orifice on another three-way through corner. Slide the tube clamp over the other rear leg.
Slide the unfitted cross-member end into the other tube clamp, slackening the grub screw, if necessary, to allow it to fit. Tighten both three-way through corners. Fit side-bracing pieces in the same way, using long tee joints on the front legs.
Stand the desk upright, fit a wooden board of choice on the top and hold the board in place with board-retaining clamps.
Follow the same procedure with different dimensions to make a stool, a meeting table, a plant stand, a footstool, a coffee table and a printer station. For a chair, the two rear legs should be about twice as long as needed for a stool, with a cross piece fitted between their upper ends. Add a board for a backrest.