Water is poured into the level and the necessary mark is placed on the surface of the wall. Then the level is pulled from both ends, and marks are placed on the tubes. After that, one of the tubes must be attached to the mark left on the wall. Then the second tube must be moved along the opposite wall up and down. At the moment when the water level stops on a line drawn in advance, this will be a place where you need to make a mark. It is important that before this the holes of the hose are closed, and the water does not spill.
