Are you 100% sure about that ?Awning is removed, install guard, re-install awning in guard.
Our Big Horn has a Dometic 9100 Power Awning. I think most of the Heartland line does. If that is what you have, it is not compatible with a aluminum cover. Look at the Dometic web page: http://www.dometic.com/USA/MS-7207-...-Rooms-Slideout-Toppers/PG-9155-Patio-Awnings