Spirit level

Tool to indicate whether a surface is level or plumb

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.

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