Levels are mechanical or electronic tools that measure the inclination of a surface relative to the earth's surface. Levels vary from simple mechanical devices to complex electronic sensors that digitally readout angular level values.

Types of Levels

There are a wide variety of levels used in industry which differ based on functionality and application. 

• Beam, box beam, I-beam, contractors, or carpenter’s levels consist of vials or electronic tilt sensors mounted in a long rectangular frame. 
• Precision frame or box levels are used for checking planarity on horizontal and vertical surfaces and shafts in machine tools and other equipment. 
• Circular or bull's eye levels use a disc shaped vial with a single bubble. Clinometers or inclinometers can indicate the angular variation or inclination from horizontal. 
• Laser levels project a spot or indicator onto a surface that is level with the projecting laser level. 
• Machinist's levels are smaller and provide a higher degree of precision compared to the common carpenters' beam or torpedo levels. 
• Line or pocket levels are small levels usually with hooks that can be hung from a line or carried in a pocket.  Plumb bobs are attached to a line to provide a vertical or plumb reference. 
• Stud or post levels often have plumb and cross test vials designed to attach to studs or posts and aid in establishing a plumb or level condition. 
• Transit or transit compass level is used for plane surveying. 
• Water, water tube, manometer, or hydro levels use leveling effect of water or another liquid to determine if two or more points separated by a large distance on a surface or surfaces are level. 
• Plumb vials are levels with a vial orientated to facilitate checking of vertical inclination or plumbness. 
• Cross vials are levels having the ability to assess level or inclination along two axes.  This capability is usually developed using two vials orientated perpendicular to each other.

Important Specifications

Important specifications for levels include the angular range, angular resolution, and length.  Displays for levels can be non-graduated meaning that the level has no direct display of figures or results.  Levels can be engineered to mount on the machine or instrument, to incorporate magnetic holding, to be linear ruled, and to be self-leveling.

Applications of Levels

Levels are used in construction and building (contractors), drafting and drawing (designers), machine shops and tool rooms (machinists), field work (surveyors), and offices.  Construction or building site levels are used by contractors, carpenters, surveyors, or builders for framing, layout, foundation construction, and various plans and projects. Machine shop and tool room levels are used by machinists, engineers, technicians or operators for layout, machine set up, and checking of surfaces or parts.  Light duty and office levels are lower precision, light weight, or lower cost measuring tools or instruments for office, residential, drafting, or other undemanding end use.  Surveying or field work levels are used by surveyors or field technologists for mapping, executing site plans, and checking building or wall surfaces.