Levels measure true horizontal (level) and true vertical (plumb) either with vials (spirit levels) or sensors (electronic levels). These mechanisms are incorporated into rails of wood, plastic, aluminum or magnesium. The rail or body of the level may be solid, I-beam or box-beam. Better grades of levels are determined by the strength and rigidity of the frame, and the type and accuracy of the vials or other measuring device.

Level vials may be adjustable or nonadjustable, straight or bent, replaceable or permanent. Some vials are constructed of a precision-tapped block of solid acrylic and are virtually unbreakable.

Electronic levels employ sensors rather than vials. One uses an audio signal or colored lights to indicate level and plumb, another includes a visual display. More sophisticated models read angles as well as level and plumb, and offer a reset button so the level can be recalibrated if dropped.

Levels come with both adjustable and nonadjustable vials. Wood levels use epoxy or cement to hold vials in place. Accidental damage can knock vials out of adjustment. Levels with replaceable vials provide on-the-spot serviceability in the event a vial is accidentally damaged.

Better wood levels come with brass or aluminum edges. These edges prevent chipping and help to protect the frame from distortion due to warpage. Better aluminum levels come with top reading windows, nonadjustable vials and protective end plates.

Levels are available in lengths up to 120". Magnetic edges are also available to free the user's hands when used around ferrous metals. Some levels use graduated vials to help determine pitch or slope.

Line levels are used where no flat surface is available. For instance, a line level can be attached to a string stretched between two points, allowing the user to make an accurate comparison of heights between the two points. Chalk lines and plumb bobs are also used to mark the distance or compare heights.

When it comes to calculating angles or dealing with sloped surfaces, some electronic levels can read roof pitches, stair slope, and drainage angles and show them on an LCD display in degrees, percent slope or inches per feet (rise/run).

A torpedo level, approximately 9" long, is used for work in close quarters. It is most popular among mechanics, hobbyists and householders.

Check your state and local codes before starting any project. Follow all safety precautions. Information in this document has been furnished by the North American Retail Hardware Association (NRHA) and associated contributors. Every effort has been made to ensure accuracy and safety. Neither NRHA, any contributor nor the retailer can be held responsible for damages or injuries resulting from the use of the information in this document.