A level is a very good tool, especially with a release. Side hill shots can be way off your aiming point if a level is not utilized. Your stance is not flat and the cant or angle of the bow compared to the angle of the hill or slope can be very deceptive. Fingers shooters have it a bit easier in that they are holding the string at a specific anchor point. Your tab on the string will level the bow IF you don't grip the handle.