A spirit level, bubble level, or simply a level, is an instrument designed to indicate whether a surface is horizontal (level) or vertical (plumb). It is called a "spirit level" because the liquid inside its vial is commonly alcohol, or "spirit". The name refers to this alcohol-based solution, which, along with an air bubble, indicates whether a surface is level or plumb. Alcohol was historically preferred over water because it has a wider temperature range, won't freeze, and provides less friction for the bubble, ensuring greater accuracy and longevity of the tool. Two basic designs exist: tubular (or linear) and bull's eye (or circular).Different types of spirit levels may be used by carpenters, stonemasons, bricklayers, other building trades workers, surveyors, millwrights and other metalworkers, and in some photographic or videographic work.
Bubble level in the context of Level (instrument)
A level is an optical instrument used to establish or verify points in the same horizontal plane in a process known as levelling. It is used in conjunction with a levelling staff to establish the relative height or levels (the vertical separation) of objects or marks. It is widely used in surveying and construction to measure height differences and to transfer, measure, and set heights of known objects or marks.
It is also known as a surveyor's level, builder's level, dumpy level or the historic "Y level". It operates on the principle of establishing a visual level relationship between two or more points, for which an inbuilt optical telescope and a highly accurate bubble level are used to achieve the necessary accuracy. Traditionally the instrument was completely adjusted manually to ensure a level line of sight, but modern automatic versions self-compensate for slight errors in the coarse levelling of the instrument, and are thereby quicker to use.
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