If the tree consists of two or more distinct trunks at this height, the circumference of only the largest trunk is measured. The circumference receives 1 point for each inch of circumference. The tangent height gauge is used by holding it parallel to the ground and viewing the top of the tree through the two guide holes. The person holding the tangent guide should move forward or backward until the very top of the tree in seen through both of the holes. Once the approximate distance from the tree is found, it may be useful for another person to assist in making certain the gauge is being held level by using the level bubble parallel.
Experienced users can level the gauge by watching the leveling bubble in the mirror.
After the tangent guide is level it may be necessary to move forward or backward some more to view the tree's top through the two holes. The tree height is equal to the sum of these two measurements, distance from the tree to the gauge plus height of the gauge from the ground. A tree receives 1 point for each foot in height. Stand directly under the outermost branches of the tree. Place a marker.