Mine just slips over and isn't secured by anything and I've never had a problem. Mine goes over really tight though, not forcing it on but, close to it.
__________________
2012 Keystone Sprinter
Still sticking around for the good people and advice.
When I bought my TT this year, I asked the dealer the same question. According to him he has never one come off unless physically removed by the owner or someone else.
i use a small bungee,. on the bottom on each side of the cover is a tab with holes. i connect it there and run it undet the tanks. More for to slow down someone taking the cove off that shouldnt