Irrespecitve of their type, all precision levels are based on long-time stabilisation and reliability, but also on a free measuring base - the centre of the earth. Due to the gravitation, the liquid with embedded bubble of gas or the gravity pendulum indicates the horizontal or vertical level based on this natural reference. Electronic inclinometers or spirit levels measure the position of the pendulum compared to the measuring faces fitted on the tool body.
From these perfect conditions, each level offers a wide number of possibilities for accurately measuring to the nearest degree. The measuring faces lying horizontally and vertically enable any deviation of the geometrical elements being measured on the workpiece to be detected. These deviations often result from straightness or flatness errors, but also from position errors like those from parallelism or squareness.