How do I install brackets to roof so I can tie down stuff?

In our younger days, we had a truck/camper with no awning. These were the days before eez-ups and many used a tarp with four poles, one at each corner. I took one of those tarps, added a third brass eyelet and then mounted three of these to the roof edge of my camper.



So one side of the tarp was held onto the roof by the hooks and I used three poles on the other end, securing the poles to the ground with cord.