A bubble level, also known as a ‘spirit level,’ (or simply a ‘level’), is a woodworking tool that determines if a surface is level or plumb. Levels are also common in masonry, stoneworking, metalworking, land surveying, and construction, among others.

How A Bubble Level Work

Levels employ a fairly simple, yet effective principle. Here’s how a spirit level works:

• Liquid and Bubble: This version consists of a narrow, transparent container (or vial), partially filled with liquid, usually ethanol. Inside the container is also a bubble of air that moves as the user positions the tool on surfaces.
• Gravity Reference: The principle behind this tool relies on gravity’s effect on the air bubble. When the tool is placed on a surface, the bubble will try to position itself at a corresponding point on the vial to determine if the object is level.
• Level Indicator: The vial has two marking lines as a reference point for determining whether a surface is level. An off-centered bubble indicates a tilted surface.
• Reading: Place the bubble evel on a surface and adjust the orientation. Once the bubble is centered, the surface is considered level.
• Plumb Measurement: Some spirit levels can also determine vertical plumb lines using additional vials set at a 90-degree angle to the main vial.

Spirit Level Types

These are various types of levels for different purposes:

• Standard Spirit Level: The most common type of bubble level used for general leveling tasks. It consists of a straight bar with a bubble tube.
• Carpenter’s Level: Common in woodworking and construction, the carpenter’s level has two vials to allow horizontal and vertical leveling.
• Torpedo Level: Also known as a pocket level or mini level, this shorter level can reach more compact spaces. The torpedo level is a favorite among plumbers and carpenters.
• Line Level: A small level that checks the levelness of a horizontal line. Line levels are useful when installing items such as shelves or cabinets.
• Post Level: Used to ensure a post or beam’s levelness during construction.
• Bull’s Eye Level: This circular level has a bubble that moves to the center of the circle when placed on a flat surface. A bull’s eye level is useful when the level of a surface needs checking from all directions.
• Digital Level: These levels incorporate digital displays to provide accurate readings in degrees or percentages. Some digital or electronic levels also have audible alerts that aid in reading.
• Slope Locator: These tools can locate slopes and inclines, especially in landscaping and grading.
• Inclinometer Level: The inclinometer level (aka clinometer) measures the angle of slope or incline. It is commonly used in surveying and engineering.
• Surface Level: Used for checking the flatness of surfaces, especially in precision machining and industrial applications.
• Cross Check Level: This bubble level comes with multiple vials at different orientations. This allows simultaneous checking of both level and plumb positions.