Doors in houses are not generally of elaborate or peculiar construction, and do not therefore call for much notice. External doors should be made of good red deal or of one of the hardwoods - oak, mahogany, &c; internal doors are sometimes made of pine, but red deal framing is better, with panels perhaps of pine, canary wood, or Californian redwood. Pitch-pine is so liable to shrink and warp that it cannot be recommended. The usual hardwoods are of course the most beautiful and durable, but their eost is often prohibitory. Undercut moulds around the panels should be avoided, on account of the difficulty of cleaning them; indeed a special panel for hospital doors has recently been designed, in which every angle and corner is rounded to prevent the lodgment of dust and germs and to facilitate cleansing. Where the ventilation of the house has been duly considered, draught-excluders, which largely prevent the entrance of dust, may with advantage be fixed on all external doors. A feature of internal doorways, which ought to be more frequently adopted for purposes of ventilation, is the hinged overlight, made to open and close at will; examples of these are given in Plate II. For large mansions, fire-resisting doors may be necessary in different parts of the building; these may be of wrought-iron or steel, or (better) of two or three thickness of wood boards covered with thin sheet metal.