The mouldings and decorations used should be in harmony with the general structure and in character with the order if one is used.
Occasionally columns or pilasters are introduced, with or without the arch, but the same general proportions apply, the aperture being two squares.
When doors are placed under arches the top line of the entablature should agree with that of the impost.
When a pediment is used, the height should be one-fourth the width of the base.
The general proportions and treatments of doors apply also to windows, and if doors and windows are placed in the same line the heads of the openings should be in horizontal alignment. If this is not possible the top of the cornice may agree with the inner line of the window openings.
Windows terminate below in a sill, or sometimes in a balcony, and as a general rule those on the same level should be similar in treatment, but an alternation such as already suggested with curved and straight lined pediments is quite satisfactory.
The frieze and consoles of doors and windows are often decorated with relief ornament.
When a façade is divided by columns or pilasters the bays are pierced with windows ranged above each
C. & D. Rustication with Horizontal and Vertical Joints Defined. ]
other, the heights varying with the different floors. Those on the first storey are usually of full height, and those above less in height and simpler in treatment. The width of apertures should be the same for the different levels, except in the case of basements, where they may be narrower.
When an order is not employed in a façade variety may be obtained by grouping the windows; or three-light windows may be introduced. The centre light, which may be treated with an arched head, should be twice the width of the side lights.
[Illustration: No. 185. Three-Light Window.]
The number of windows in a façade should be odd, so that there may be a centre one, and the end windows of a range should be kept well clear of the angles of the building.
In interior decoration surfaces such as walls and ceilings may be divided into panels of various shapes by a system of framing. The form of the framing may be rectangular, square, polygonal, circular or oval; and the panel is generally recessed from the dividing stiles and rails or ribs, while the latter are frequently supplemented by mouldings.