This official handbook of the U.S. Forest Service explains how to use the Abney hand level, a clinometer tool used to measure angles in various natural environments. The Abney tool was invented by William de Wiveleslie Abney during the 1870s. By the time the device was recognized and widely-used in the early 20th century, it had been refined. Though earlier guides cover its basic usage, this U.S. government commissioned handbook offers demonstration...