I assume he wants drawings of the roof and bars, so that he can build a rack - at least that's what he says.
Sometimes I don't bother to answer because the answers bring controversy - somethings you just need to get your tape measure out and start on it yourself. My first "rack" was two lengths of 2"x2" softwood notched with a handsaw to fit across the rails - and no measurements were taken, I dropped the wood across the rails and marked it with a pencil.
The "bars" went on the rails, two doors went on the bars, and two ratchet tiedowns held the entire kit & caboodle on to the rails - I used those wooden bars for many months until I found bars that I liked.
