Generally speaking, the detail should preferably be of a formal character, and should consist of the repetition of units with no interest beyond that imparted by alternation.
The detail must, moreover, be designed with due regard to the space to be filled, and, in any border which encloses any space, a common divisor of height and width should be found in accordance with which the unit can be designed.
[Illustration: No. 207. The Evolute Scroll as a Border.
The meeting angles or corners of borders invariably require special treatment, and in those positions the detail should be compact and stronger in appearance than the general pattern. The simplest expedient is some form of patera or rosette, but, whatever the detail, it should always be in strong contrast to that of the run of the border. The only forms that can be continuous without any marked change in the angles, are the undulating stem, the wave, and its square form the key or labyrinth; but even with these the proportion of width to height at times needs modification. If a common divisor is not possible, the difficulty can to some extent be overcome by making the form reciprocal and letting the two sides meet in the centre of the border, so that any slight disparity in treatment and dimensions will not be noticeable.
As the Pilaster is used structurally in order to give support, so its treatment in interior decoration must conform to architectural requirements, and the decoration should be symmetrical on a central axis and vertical in direction.
When flutes are employed to decorate the pilasters, they should be unequal in number--seven being a favourite number. The flutes may be further decorated by cabling, though this should extend to only one-third of the height. The cabling can be elaborated into a series of husks which may arise from the base or be pendant from the top of the pilaster. In either case the general rule must be observed that the cabling shall occupy only a third of the total height.
Sunk panels are also used for decorating pilasters. They cover about half the width, and are moulded at the edges. In some instances, notably in pilasters of the Early French Renaissance, the panel is broken in the centre by the introduction of a smaller circular or lozenge-shaped panel. Sometimes the panel is adorned with floral or other detail, and this should be symmetrically arranged on a central axis. For this purpose the undulate stem should never be employed. Such detail requires a start at the base and a definite finish at the top of the pilaster, but for the rest, it may consist of the same unit repeated, or of two alternating units.