пузырьковый уровень(прибор: A spirit level, bubble level, or simply a level, is an instrument designed to indicate whether a surface is horizontal (level) or vertical (plumb).wikipedia.org)
магнитный пузырьковый уровень(Klein Tools 935L Level, 24-Inch Magnetic Bubble Level with Adjustable Vial and Top V-Groove, High Viz Orange (Amazon.com)'More)