This handy little instrument helps to figure quickly and accurately the heights of poles, trees, buildings or conductor clearance. A lineman can be taught in a few minutes to use it. The diagram shows how it works. Sight point A through the Teleheight and move backward or forward until the bubble centers on the hair line, which will be point C. Measure distance from C to D and add distance BC to find correct height. Leather case (21/4″ x 41/4″) has belt loop.