Final Answer:
Use a spirit level to determine if a surface is exactly horizontal.
Step-by-step explanation:
A spirit level, also known as a bubble level or simply a level, is a tool used to determine if a surface is level or horizontal. It typically consists of a transparent tube filled with liquid and a bubble. When the level is placed on a surface, the bubble will move to the center if the surface is level. This tool is widely used in construction, carpentry, and various DIY projects to ensure that surfaces like floors, shelves, or countertops are perfectly horizontal.
Using a spirit level is a straightforward process. The level is placed on the surface to be checked, and the user observes the position of the bubble within the tube. If the bubble is centered between the marked lines, the surface is level. If not, adjustments can be made until the bubble is centered.