The 0 degree is for when you are working over say a flat roof and the angle you need is in the pole.that meens you are standing away fron the glass. If you a crank angle at the top of your pole you can tip the crank say to 50 degrees and place the squeegee at rigt angle ti our pole length and work across the glass left to right.If you work direct below your window then the 30 degrees will be fine across or just down strokes.