To check the levels of two points that are widely separated, use a clear flexible plastic pipe, or a hosepipe with clear plastic tubes fitted in each end. This method is especially useful for checking levels round a corner.
Fill the pipe with water and position and fix one end of it against the required level with the water in the pipe virtually flush with the pipe opening. Place the other end against a batten fixed vertically at the point where the level is being assessed and raise or lower the hosepipe until the water level is again virtually flush with the end of the pipe. Mark the level on the batten. When taking a leve1 in this way. Always have a can of water available to make good any spillages from the hosepipe during the process.