The opening up of large horizontal areas for excavation, used especially where single period deposits lie close to the surface. It is the excavation of as large an area as possible without the intervention of balks and a grid system. This technique allows the recognition of much slighter traces of ancient structures than other methods. On multi-period sites, however, it calls for much more meticulous recording since the stratigraphy is revealed one layer at a time. In this method of excavation, the full horizontal extent of a site is cleared and large areas are open while preserving a stratigraphic record in the balks between large squares. A gradual vertical probe may then take place. This method is often used to uncover houses and prehistoric settlement patterns.