My coop is 4'x8'. I am using 2x4's. After I have the footers and framing done I need to build my roof. I have no idea how to go about figuring the angles to cut my rafters (I think that is what each piece is called), and I don't have a clue as to what length to cut each piece so they meet in the middle. When I get the framed walls up the coop should be 4' wide from outside to outside meaning the outside of each frame board. I am no good at geometry at all. I can tear a piece of electro-mechanical piece of equipment apart and rebuild it, but this cutting and angles just don't click in my head so please make this as elementary as possible.