To those of us, who are new to the molding world, in addition to accurately determining the angle in degrees to a tenth of a degree on anything you need a measurement on, it has this cool built in crown molding feature. First you determine the spring angle, (which is the angle the crown molding sits on the wall). With the tool in place you press the button, it memorizes the spring angle which is shown in degrees, and the letters SPR appear. Then place the tool on the corner where the molding is to be installed, it displays the corner angle in degrees, press the button again, the letters CNR appear. Simply press the button once again, and it automatically calculates the Mitre Angle to set your Mitre saw, and by pressing the button once again, it gives you the bevel angle to set saw to as well. Lay your molding flat on your COMPOUND mitre saw and cut perfect moldings every time. If your saw has dead on accurate gauge settings according to the scales, then all you have to do is dial it in, and cut away, if not this Bosch unit will give you the ability to set your saw accurately as well.  Another reason why this tool is so important, is that a lot of walls are not really set at a true 90 degrees, so a detent setting on your saw, at the common crown molding setting, is not always the proper angle.