12 ©2018 Johnson Level & Tool - Rev. 1
7. Checking Accuracy
IMPORTANT: It is the responsibility of the user to verify the
calibration of the instrument before each use.
Plumb Accuracy Check
Plumb accuracy can be checked in two ways. The easier, though less
accurate, method is to project the beam on a flat wall and use a
plumb bob to check the plumb of the beam.
The more accurate method to check the plumb line accuracy is to
follow these steps:
1. Place the laser on the floor in a fairly
dark room, approximately 10′ from a
doorway.
2. Project the plumb beam through the
doorway.
3. Mark the plumb beam’s closet point to
the tool on the floor as Point 1.
4. Mark a spot 20′ away as Point 2.
5. Mark directly under the doorway as Point C.
6. Mark a spot directly above Point C, but on the doorway, as point D.
7. Move the laser to Point 2, and aim the plumb beam directly
through Point 1 and Point C.
8. Mark on the doorway Point E.
9. Measure the distance between Point D and Point E. If this
distance does not exceed 1/8″ for a 10′ high doorway, then the
tool is properly calibrated.
2891i-1English_Manuals 6/4/18 10:24 AM Page 12
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