Which tool helps determine if a surface is level or plumb?

The carpenter's level is a specialized tool designed specifically to determine if a surface is level (horizontal) or plumb (vertical). It typically consists of a long, straight beam with one or more air bubbles contained in glass vials along its length. The bubbles float in a liquid and indicate the level of the surface by showing whether the bubble is centered between the marked lines. When the bubble is centered, it signifies that the surface is perfectly level or plumb.

This tool is essential in various construction and carpentry tasks where accuracy is crucial, ensuring that structures are built correctly and maintaining aesthetic alignment. The other tools mentioned serve different purposes; for instance, a carpenter's square is used for marking and checking right angles, a micrometer measures small distances with great accuracy, and a sliding bevel allows for adjusting angles, but none of these perform the function of checking if a surface is level or plumb.