A chair is a raised surface used to sit on, commonly for use by one person. Chairs often have the seat raised above floor level, supported by four legs. A chair with arms is an armchair and with folding action and inclining footrest, is a recliner. The design may be made of porous materials, or be drilled with holes for decoration; a low back or gaps can provide ventilation. The back may extend above the height of the occupant's head, which can optionally contain a headrest.