How to use string action gauge

1. Orange line is started from 1.0 mm height to 2.0 mm. Green line is started from 2.0 mm to 3.0 mm.
2. The cross point of blue line and orange line is 1.0 mm and the cross point of yellow and orange is 1.2 mm.
3. Red line is the bottom of string and red line is crossing to green line. You read the cross point of red and green.
<4. This cross point of green and red is yellow line (0.2 mm line). So the string height is 2.2 mm.