Which tool is commonly used to level surfaces?

The tool commonly used to level surfaces is the level. A level serves the specific purpose of determining whether a surface is perfectly horizontal (for a level) or vertical (for a plumb). It typically consists of a sealed glass or plastic tube filled with liquid, with an air bubble inside. When the bubble is centered between the lines on the level's scale, it indicates that the surface is even. This accuracy is essential in various construction and carpentry tasks, where ensuring proper alignment is critical for structural integrity and aesthetics.

The square, while useful for checking right angles and ensuring that components are square to each other, does not measure levelness. The caliper measures dimensions such as thickness or diameter but does not have any capability related to leveling surfaces. The measuring tape is primarily used for measuring lengths and distances, lacking the functionality necessary to assess levels. Thus, the level is the right tool for achieving a flat or vertical reference point in construction and related tasks.