These are training tools that will help you learn to draw and they are especially useful for learning perspective and proportion.  These were designed by Dr. Betty Edwards and exclusively sold by DRSB.  This package includes two important sighting tools:  the ProportionFinder and the AngleFinder.  The ProportionFinder is a measuring device to help you achieve proportionally accurate drawings.  The AngleFinder will help you see difficult-to-assess angles; it essentially is a protractor but designed for drawing.