The spirit level is a widely used tool by many professions, including carpenters, stone masons and the occasional photographer, as well as homeowners engaged in do-it-yourself projects. Spirit levels, or bubble levels, come in all shapes and sizes. The most common is the tubular spirit level. Spirit levels are also found on tripods, known as a bull's eye spirit level. They're easy to use, and can be employed for a variety of tasks.
Test the spirit level to make sure it is calibrated. This can be done by placing the spirit level on a level surface and visually confirming that the bubble is in the centre of the two lines on the spirit tube. Turn the level around and replace on the same surface. The bubble should not have shifted in any direction. Repeat for each tube on the level, assuring that the entire level is accurately calibrated.
Place the spirit level on the object or surface that you wish to be perfectly horizontal (level), or vertical (plumb).
Adjust the spirit level until the bubble is centred between the two lines. This is done to get an idea of how much the object or surface must move to become level or plumb.
Adjust the object until it is level or plumb, according to the level.