"Procoelous" vertebrae are anteriorly concave and posteriorly convex. Hollow ground blades have concave, beveled edges. The nail clipper consists of a head which may be concave or convex. Points where concavity changes (between concave and convex) are inflection points. A lens with one convex and one concave side is "convex-concave" or "meniscus". The head was encircled by a frame, optionally composed of convex, concave and straight lines. The kidney is a bean-shaped structure with a convex and a concave border. The surface may be either "convex" (bulging outward) or "concave" (recessed inward). The throne hall stands on a high base with convex and concave moldings. They have convex and concave regions that produce deliberately distorted images. It uses a convex lens as the eyepiece instead of Galileo's concave one. Submodular functions have properties which are very similar to convex and concave functions. It was a curved, knife with the edge on its concave side. This means that they were convex from the front and concave from behind. An implementation that keeps separate lists of convex and concave vertices will run in time.