Now like I said I've never done anything like this so now I need help. Wanna do a lean to like style roof. I cut 4 rafters to go across the roof line. Was thinking maybe a 12" rise on one side down to a 6" rise o the low side. How do I cut the angle? What degree? I'm using a chop saw. I just tried a 30 degree cut on sum scrap & I'm way off. Need help!!!!