I wondered about that too. I decided it must fasten there somehow, maybe by transitioning to something flat and thin enough to tuck under the roof edging. Or maybe to suction cups. There was no explanation, nor did I see another picture of the setup, and I've lost the link I had. It was posted on the "alinerchaletaframes" group, one of the Yahoo Groups. I see a lot of postings there of workarounds for problems, how-tos including complete rebuilds, and mods folks have made. No charge to join and they don't ask what brand you have or even if you have an Aframe at all. You do need a free Yahoo account.
It's never too late to have a happy childhood!
Lee, WU0V, and Courtenay, N0ZDT
2011 Rockwood A128
2000 Silverado 1500 pickup
60W solar system
2000W inverter generator