Block or brick partially embedded in a wall, with one end projecting out from the face. The weight of added masonry above counterbalances the cantilever and keeps the block from falling out of the wall. Corbeling often occurs over several courses, with each block or brick overhanging the one below so as to resemble a set of inverted steps. The form may be continuous, as in a corbeled arch, or a series of separate brackets, as on a medieval battlement. Corbeling was used extensively before the development of true arches and vaults.