Frames, bases, springs, hardware, ornamentation, seats, legs and entire structures may be of metal. Tubes are sometimes filled with sand or spring-like inserts to prevent crushing. Metal joints can be welded or mechanical. Resistance welding passes an electrical current through the metal, fusing the parts at the contact point. Spot-welding produces a small, round joining at a particular location.
Mechanical joints require rivets, screws, bolts and nuts and a variety of special fasteners.
With the exception of stainless steel, metals need to be finished to eliminate rusting or oxidizing. A variety of natural materials have been used in furniture construction over the years. Materials often are determined by the locality of the builder. Common are rattan, bamboo, wicker and buri. The structures of these pieces are quite similar.