Follow these steps to return the gauge needle to zero

1. Unscrew (counterclockwise) and remove the lens from the gauge (the red peak-hold needle is attached to the lens)
2. Remove the handle (to prevent applying pressure during this process)
3. Place the instrument on a sturdy surface
4. Using a small, slotted screwdriver, rotate the slotted screw counterclockwise in the gauge dial face until the needle is below zero (if it is already zero, turn the cam until it is slightly farther below zero)
5. Turn the screw in the reverse direction until the gauge needle is almost touching the zero line
6. Reattach the gauge lens and the handle
7. Pick up and squeeze to apply pressure to the instrument a few times
8. Place the instrument back on a sturdy surface and return the red peak-hold needle to zero by turning the center knob
9. Check to see that the red peak-hold needle is at zero
10. If the red peak-hold needle is not on zero, repeat steps 1-10 until the red peak-hold needle is at zero