A spirit level is a tool used in construction, woodworking, and other fields to determine whether a surface is level or plumb (vertically straight). It typically consists of a rectangular or cylindrical frame with one or more bubble-filled vials of liquid inside. The vials are curved and mounted so that the bubble inside will center itself when the frame is level or plumb.
To use a spirit level, the tool is placed on the surface to be checked, and the frame is adjusted until the bubble inside the vial(s) is centered. This indicates that the surface is level or plumb. Spirit levels can be used to check the levelness or plumbness of walls, floors, beams, and other surfaces in construction projects, as well as for measuring the slope or grade of a surface.
