What type of tool is a 'spirit level'?

A spirit level is specifically designed to determine whether a surface is horizontal (level) or vertical (plumb). It contains a sealed tube filled with liquid and a bubble that moves within the liquid; when the bubble centers itself between two marked lines, the surface is considered level. This tool is essential in construction and carpentry for ensuring that structures are built correctly and will not warp or shift over time. Its primary function as a leveling device distinguishes it clearly from the other options, which serve entirely different purposes. A measurement tape is used for measuring lengths, a cutting tool is meant for cutting materials, and a fastening device is for joining two or more items together, none of which involve leveling surfaces.