In fortification the excavation in front of the parapet of any work, ranging in width from a few feet in field fortification to thirty or forty yards in permanent works, having its steep side next the rampart called the escarp: the opposite one is the counterscarp. Its principal use is to secure the escarp as long as possible. There are wet ditches and dry ones, the former being less in favour than the latter, since a dry ditch so much facilitates sorties, counter-approaches, and the like. That kind which may be made wet or dry at pleasure is most useful.