In order to make furniture out of old cardboard boxes, you will need cardboard boxes, rods, nuts, and washers. Cut many pieces of cardboard in the shape of an L. When you have enough cut pieces to make a chair the size that you want, begin fastening the pieces together, by pushing a long rod through them at the base and front. Once you've strung them all together, tighten them with a washer on the ends. Do this at both ends. When you are done, you will have a functioning chair. This same technique may be used to make other furniture from cardboard or other chairs styles.