What is a Builder's Level? How do Builder's Levels Work?

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A builder's level is used in the construction field to set up level points and to check elevations. It is an optical instrument used mainly in surveying and building but is also useful for transferring, setting, or measuring horizontal levels. The tripod the builder's level is being set up on must be set on secure ground to get the telescope positioned level.

Also called a "dumpy" level, the builder's level is inexpensive, easy to assemble, easy to use and lightweight. There are many parts to a builder's level, but it is primarily a leveling vial attached to a telescope. The leveling vial consists of marks called graduations used for centering the bubble. A builder's level works by attaching the telescope to a leveling head and finally mounting to a tripod.

Builder's Level vs Transit Level

Builder's levels work similarly to transit levels, with one important distinction. When the telescope of a builder's level is locked into place, it works nearly like a transit level. When a builder's level is not locked into place, however, it can move in a complete circle on a horizontal plane. Conversely, when a transit level is not locked into place, it can only tilt on a vertical plane and has a limited range of mobility.

Key Terms

  • Benchmark - permanent or fixed point with a known elevation.
  • Height of Instrument - how high above the bench mark the telescope sits after being leveled.
  • Station - definite point between which lengths are measured. When the instrument is moved, each new location becomes a station.
  • Turning Points - intermediate points used for transferring a known elevation.
    • Backsight - the measurement taken when the instrument, in the level position, is directed "back" toward the bench mark. Always recorded as a plus-sight because a back-sight is always added to the known elevation in order to record the height of the instrument.
    • Foresight - the measurement taken when the instrument, in the level position, is directed away from the bench mark. Always recorded as a minus-sight because it is always subtracted from the instrument height. This new measurement creates another bench mark.

Parts of a Builder's Level

A builder's level consists of many parts:

  1. Telescope - holds lenses which magnify objects in the sight.
  2. Graduated Leveling Vial - used to level the telescope on its base.
  3. Graduated Horizontal Circle - marked by degrees, used for setting and reading angles.
  4. Leveling Screws - allows adjustments to be made to ensure the instrument is level in all positions.
  5. Focusing Knob - can be turned to make object appear crisp and clear.
  6. Base - area where the builder's level attaches to the tripod.
  7. Eyepiece - located at viewing end of telescope, can be turned to bring the crosshairs into focus.
  8. Horizontal Clamp Screw - holds the instrument in the horizontal position when tightened.
  9. Horizontal Tangent Screw - allows the instrument to be adjusted horizontally.
  10. Vernier Scale - moves when the telescope is turned to the left or to the right.


The telescope is located at the top of the builder's level. The telescope's main purpose is to magnify distant objects and make them look nearer. The telescope moves horizontally around a graduated horizontal circle. The horizontal circle is marked at each 1 degree up to 360 degrees.

The objective lens sits at the end of the telescope. It catches the object being sighted and with the help of other lenses inside of the telescope, the object gets magnified.

At the opposite end of the objective lens sits the eyepiece where the user looks. Inside the eyepiece, crosshairs run horizontally and vertically. Rotating the eyepiece allows the crosshairs to become more focused and clear. There is a focusing knob located on the barrel of the telescope used to focus crisply on the object being sighted.

Stadia lines are located on the eyepiece. Stadia lines are short horizontal lines located above and below the crosshair that runs horizontally. The stadia lines get bisected by the vertical crosshairs which allows for the user to find the distance of the object being sighted.

Level Vial (Graduated Leveling Vial)

Also known as a spirit level, the graduated leveling vial is used to level the telescope while being placed on the base. This works much like a traditional hand spirit level.

The base plate of the builder's level is the area which the level is attached to the tripod. There are three different kinds of base plates, all with specific instructions for attaching instruments. When using a threaded instrument base, it can be screwed to the threaded tripod head. When using either a flathead or a dome head tripod, there is a center bolt that is located on the bottom of the tripod that will need to be screwed into the level.

Preparing to Use a Dumpy Level

When preparing to set up a builder's level, make sure you have the right tripod since tripods can have different types of heads.

  • When using a 5/8" center bolt mount: the protective cap from the tripod head should be fitted onto any of the tripod's legs using the attachment found on the cap.
  • When using a threaded tripod head mount: remove the threaded protective cap and set aside. Unthread the level from the case mount and screw on the tripod head. After being connected to the tripod head, thread the protective cap onto the case mount.

Once you have found the correct head for your instrument, you can start your set up.

Mounting a Builder's Level

Place the level directly on the tripod head after removing the level from the carrying case. If the level is placed elsewhere, it could lead to instrument damage. After placing it on the tripod, the next step is threading or bolting onto the tripod base. Remove the protective lens covers and put them in the carrying case. You should also place the sunshade on the telescope. After these steps, the mounting process is finished.

Builder's level from Johnson LevelHow To Use a Builder's Level

  1. Make sure that the tripod is stable and securely planted before setting up the builder’s level. 
  2. Tighten the attachment between the builder's level and tripod.
  3. Ensure the four leveling screws are not too tight against the leveling base plate.
  4. First position: line up the telescope until it is located directly over a pair of leveling screws.
  5. Using the leveling screws, center the bubble in the spirit vial.
  6. Placing both of the leveling screws between your thumb and forefinger, turn both screws at the same time in opposite directions and watch for movement in the graduated spirit vial.
  7. Move the thumbs together in or out. The bubble will follow the left thumb.
  8. Second position: when the bubble is centered, rotate the telescope 90°.
  9. Repeat the thumbs in, thumbs out action until the bubble is centered in the second position.
  10. Turn the telescope back to the first position and make the proper adjustments to ensure that the instrument is still level.
  11. Move the instrument through various stages of the 360° and check if the instrument is level at all points.
  12. Focus your builder’s level by aiming your telescope at an object. It should look blurry at first, but turning the eyepiece either left or right should make the object appear clearer.
  13. After focusing the eyepiece, point the level directly at the specific target. 
  14. Keeping the crosshairs in focus, use the focusing knob to make the specified object appear sharp.
  15. You are ready to make accurate measurements.

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Optical level from Johnson LevelHow to Check a Builder’s Level

  1. Inspect your builder’s level. Is there any damage? Are any parts broken?
  2. Get a 100+ foot tape measure and two measurement rods. You’ll need to be in a large, open area. The flatter, the better.
  3. Set up the builder’s level on a tripod.
  4. Locate the thumb screws and turn them to adjust the vials to center.
  5. Measure 100 feet from the builder’s level in opposite directions. Place measurement rods at each spot.
  6. Read the measurement of the first rod through the builder’s level. Confirm it measures 100 feet.
  7. Read and record the distance to the second rod.
  8. If the two distances read the same through the builder’s level, your level is calibrated.
  9. If not, your unit needs to be calibrated. Read on to find out how to calibrate a builder’s level.

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Builder's level by Johnson LevelHow to Calibrate a Builder’s Level

  1. If you’ve already checked to see if your builder’s level needs calibration, skip to step 9.
  2. Closely inspect the builder’s level. Is there any damage? Are any parts broken?
  3. Get a 100+ foot tape measure and two measurement rods. 
  4. Set up the builder’s level on a tripod.
  5. Locate the thumb screws and turn them to adjust the vials to center.
  6. Measure 100 feet from the builder’s level in opposite directions. Place measurement rods at each spot.
  7. Read the measurement of the first rod through the builder’s level. Confirm it measures 100 feet.
  8. Read and record the distance to the second rod.
  9. If the two distances read the same through the builder’s level, your level is calibrated.
  10. If not, adjust the vials from step 4 half the difference in the two measurements.
  11. Repeat the measurements.
  12. Repeat the process (steps 6-8) until the distances read the same.

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Marking a Reference Line

A level grade line, or reference line, is a sight line that is established through the telescope. It is created at the horizontal crosshair and requires two workers to establish.

  1. The operator looks through the eyepiece of the telescope while an additional worker holds a graduated staff or tape measure vertical at the point under measurement.
  2. The instrument and staff are used to gather or transfer elevations during site surveys and building construction.
  3. Measurement starts from a benchmark with known height, or an arbitrary point with an assumed height.

Helpful Hints for Builder's Levels

  • When the objective lens is not in use, it should be covered with a lens cap to prevent damage to the equipment.
  • Detachable sunshades are useful in preventing glare and protecting the objective lens.
  • Do not lift your level by the telescope; always be sure to lift it by the base.
  • Make sure to turn both screws at the same time and rate when leveling a builder's level.
  • Make sure the builder's level is level around all 360 degrees of direction; if this is not done, the measurements will be incorrect.
  • Make sure the leveling screws are not too tight - over tight screws need to be loosened for the most accurate results.
  • Do not look at the sun through the telescope.
  • Keep both of your eyes open when looking through the telescope. This will avoid tiring your eyes and eliminate squinting.
  • The image being sighted will be sharpest when it is quartered by the crosshairs. This is the most accurate place on the lens.
  • The jumping of an image is called "parallax". With each movement, adjust the focusing knob until the image stops jumping.
  • Do not touch the tripod at anytime after the builder's level is mounted. This can cause problems with the measurements as well as the accuracy of the level.
  • In the case of a threaded base, the instrument must be unscrewed before it is removed.
  • While unscrewing the threaded base, make sure you hold the instrument with one hand. Also, make sure you hold the instrument by the frame.

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