Balustrades are sometimes used above the cornice of a building, and their height should not be more than four-fifths or less than two-thirds the height of the entablature. This height would be exclusive of the plinth on which the balusters are raised. The height of the plinth is determined by the height of the building, and the projection of the cornice, as its purpose is to raise the balusters so that they may be seen from the ordinary point of view. The principal dies may be placed over columns or pilasters and should be equal in width to the upper diameters of these, though flanking half dies may be used in addition to avoid an appearance of thinness. The plinth and capping mouldings always follow the plan of the principal dies, and are carried in unbroken lines across each interval. When the height of the balustrade does not conform to the orthodox proportions the method of determining the relative proportions is as follows:--The height is divided into seven parts; of these one part gives the height of the capping, four the baluster and two the plinth. The mouldings in character and detail are the same as those of the pedestal, and should be in harmony with the order used. When balustrading forms part of a stair, the height on landings should be three feet two inches. On the rake two feet ten inches from the step at a line vertical with the face of the riser. The plinth is invariably used as a string enclosing the ends of the steps and following the rake or angle in a straight line, and carried to the levels by means of curving ramps. In interior work the bulbous shafts of balusters are often decorated with carved detail, and the mouldings also may be enriched. _Use of Columns_ Columns were originally used in the porticos and courts of temples and other buildings, and sometimes to form supports for vaulted roofs. Wherever employed their function was directly structural, but this was not the case at the time of the Renaissance. The requirements demanded by widely different social conditions led to their being used more as decorative than structural features. The use of engaged columns and pilasters in a façade can be justified to some extent. Although such columns and pilasters may not be absolutely essential for support, yet they act as buttresses and add to the strength of the structure with a certain economy of material. Also they are æsthetically satisfactory in their effect of light and shade. _Disposition and Spacing in Colonnades_