A level is an optical tool used to determine or check points in the same horizontal plane in a process known as leveling, and is used in conjunction with leveling personnel to determine the levels of relative heights of objects or markings. It is widely used in surveillance and construction to measure height differences and to transfer, measure and determine heights of known objects or markings. Levels are devices whose construction is based on the principle of horizontal visas (levels). The level difference between the points is obtained directly, depending on the heights a and b of a horizontal visa, read on the groom held vertically at those points. Geometric or direct leveling is a method of determining level differences, which is based on the principle of horizontal visas, depending on which the elevations of the points on the earth's surface are calculated. The basic principle of leveling is the way of determining the level differences between points.