To control the horizontal position of the parts and elements of building structures typically use a bubble level. To as, for example, to check the position of the roof ridge or panels, the spacecraft that are set to make the level impossible! The easiest level for these cases — conventional PVC tube with a diameter of 6 mm, better transparent. Fill it with water, directing the open ends up. According to the principle of communicating vessels, the level in both the knees are set at the same height, and hence the line connecting them will always be strictly horizontal.
I. KONOPLENKO, V. Lepetykha village, Kherson region.