A level slope is used to install pipes on various surfaces like walls, foundations, and ceilings. The line levels are used when hanging pipe lines in an upright position and they allow you to see the center of the hanging pipes. The plumb bob is held over a vertical surface with a clamp or screw, allowing the user to read the bubble within the scale. As the plumb bob moves up and down it reads from left to right when looking at it from above or below.