FIGURE 1
HOW TO CHECK ACCURACY OF THE HORIZONTAL VIAL ON A KNOWN LEVEL SURFACE

1. Place your level on a flat surface.
2. Read the center vial and note the position of the bubble relative to the lines in the vial.
3. Turn the level 180° (end to end) and place the level in the same spot on the flat surface.
4. Read the center vial and note the position of the bubble again. If the bubble is in the exact same place, the level is accurate.
5. If the bubble is not in the same place, proceed to Figure 2, Step 1

FIGURE 2
HOW TO CALIBRATE THE HORIZONTAL VIAL ON A KNOWN LEVEL SURFACE

1. Leave the level in the horizontal position from Figure 1, Step 5.
2. Use a #2 Phillips® screwdriver to adjust the horizontal vial screw until the bubble returns to the center of the vial.
3. Turn the level 180° (end to end) and place the level in the same spot on the flat surface.
4. Read the center vial and if needed, adjust the center vial screw until the bubble is centered in the vial again.
5. Repeat these steps until the center vial bubble returns to the exact spot after rotating the level 180°.
6. Your level is now calibrated.

FIGURE 3
HOW TO CHECK ACCURACY OF THE HORIZONTAL VIAL ON AN UNLEVEL SURFACE

1. Place your level on a flat surface
2. Read the center vial and note the position of the bubble relative to the lines in the vial.
3. Turn the level 180° (end to end) and place the level in the same spot on the flat surface.
4. Read the center vial and note the position of the bubble again. If the bubble is in the exact same place, the level is accurate.

FIGURE 4
HOW TO CALIBRATE THE HORIZONTAL VIAL ON A FLAT BUT UNLEVEL SURFACE

1. With the level in a horizontal position, use a #2 Phillips® screwdriver to adjust the horizontal vial screw until the bubble moves half-way to where it was when you originally viewed it.
2. Turn the level 180° (end to end) and place the level in the same spot on the flat surface and read the horizontal vial. The bubble should now appear in the same location as the previous reading.
3. If the bubble is not in the same location, turn the level 180° (end to end) to the original starting position and turn the same screw to adjust the vial.
4. Repeat the above steps until the bubble returns to the same spot after a 180° (end to end) rotation.

FIGURE 5
HOW TO CHECK ACCURACY OF THE VERTICAL VIAL ON A KNOWN PLUMB SURFACE

1. Place your level on a vertical surface.
2. Read the plumb vial in question and note the position of the bubble relative to the lines in the vial.
3. Flip the level (side for side) and place the level in the same spot on the vertical surface.
4. Read the plumb vial again and note the position of the bubble. If the bubble is the exact same place, the level is accurate.
5. If the bubble is not in the same place, proceed to Figure 6, Step 1.

FIGURE 6
HOW TO CALIBRATE THE VERTICAL VIAL ON A KNOWN PLUMB SURFACE

1. With the level in a vertical position, use a 1/4" hex key to adjust the plumb vial screw until the bubble returns to the center of the vial.
2. Flip the level (side for side) and place the level in the same spot on the vertical surface.
3. Read the plumb vial and if needed, adjust the plumb vial hex screw until the bubble is centered in the vial again.
4. Repeat these steps until the plumb vial bubble returns to the exact spot after flipping the level
5. Your level is now calibrated.

FIGURE 7
HOW TO CHECK ACCURACY OF THE VERTICAL VIAL ON A VERTICAL BUT NOT PLUMB SURFACE

1. Place your level on a vertical surface.
2. Read the plumb vial in question and note the position of the bubble relative to the lines in the vial.
3. Flip the level (side for side) and place the level in the same spot on the vertical surface.
4. Read the plumb vial again and note the position of the bubble. If the bubble is the exact same place, the level is accurate.
5. If the bubble is not in the same place, proceed to Figure 8, Step 1.

FIGURE 8
HOW TO CALIBRATE THE PLUMB VIAL ON A VERTICAL BUT NOT PLUMB SURFACE

1. Leave the level in the vertical position from Figure 4, Step 5.
2. Use a 1/4" hex key to adjust the plumb vial hex screw needing adjustment so that the bubble moves half-way to where it was when you originally viewed it.
3. Read the plumb vial and if needed, adjust the plumb vial hex screw until the bubble is centered in the vial again.
4. Flip the level (side for side) and place the level in the same spot on the vertical surface and read the plumb vial. The bubble should now appear in the same location as the previous reading
5. If needed, repeat the above steps until the bubble returns to the same spot after you flip the level side for side.