The Silva Inclinometer 131 is a very popular and sturdy Dual Scale Clinometer for many types of uses. Measure Pitch & Roll, Incline and Slope. With two scales, one +/- 35° and a fine scale of +/- 5°. Used on sailing boats for checking heeling and on powerboats for the power trim check. Also used by geologists for checking rock face angles or fit into Earth works machinery as a guide.