Chorobates

A chorobates (Greek χωροβἀτης from khŏros; "place" + -batos, "going") was a kind of level used in classical antiquity. It was composed of a wooden frame, made in the form of a beam which was fitted with a water level, and two supports at the end of the beam. It is described by Vitruvius (Lib. viii). It is believed to be the instrument that was used to level the Roman aqueducts. The beam had a plumb bob at each end so that it could be placed square on the ground. A groove was made in the top of the beam for use as a sightline, and the beam was parallel to the water level. It enabled levels to be found between two points, and hence a series of levels when planning and surveying the path for an aqueduct.