primarily a means of hiding or weather-sealing a joint, purely decorative, or some combination of the three. As decorative elements the contrast of dark and light areas gives definition to the object. If a vertical wall is lit at an angle of about 45 degrees above the wall (for example, by the sun) then adding a small overhanging horizontal moulding, called a fillet moulding, will introduce a dark horizontal shadow below it. Adding a vertical fillet to a horizontal surface will create a light vertical shadow. Graded shadows are possible by using mouldings in different shapes: the concave cavetto moulding produces a horizontal shadow that is darker at the top and lighter at the bottom; an ovolo (convex) moulding makes a shadow that is lighter at the top and darker at the bottom. Other varieties of concave moulding are the scotia and congé and other convex mouldings the echinus, the torus and the astragal. Placing an ovolo directly above a cavetto forms a smooth s-shaped curve with vertical ends that is called an ogee or cyma reversa moulding. Its shadow appears as a band light at the top and bottom but dark in the interior. Similarly, a cavetto above an ovolo forms an s with horizontal ends, called a cyma or cyma recta. Its shadow shows two dark bands with a light interior. Together the basic elements and their variants form a decorative vocabulary that can be assembled and rearranged in endless combinations. This vocabulary is at the core of both classical architecture and Gothic architecture. Design Classical Mouldings When practiced in the Classical tradition the combination and arrangement of mouldings are primarily done according to preconceived compositions. Typically, mouldings are rarely improvised by the architect or builder, but rather follows established conventions that define the ratio, geometry, scale, and overall configuration of a moulding course or entablature in proportion to the entire building. Classical mouldings have their roots in ancient civilizations, with examples such the 'cornice cavetto' and 'papyriform columns' appearing in ancient Egyptian architecture, while Greek and Roman practices developed into the highly the regulated classical orders. Necessary to the spread of Classical architecture was the circulation of pattern books, which provided reproducible copies and diagrammatic plans for architects and builders. Works containing sections and ratios of mouldings appear as early as the Roman era with Vitruvius and much later influential publications such as Giacomo Barozzi da Vignola's,