You can also go to a hardware store and buy the spring clips for holding brooms, hoes, etc. I used four of these attached to a bay ceiling in my Itasca to store the extension. It kept it up out of the way, not taking up any storage space. Our current rig has a full length ladder, so I'm not having to store an extension.
Dan & Ro with two Rescued Boston "Terrorists"
2015 Tiffin Allegro RED 38QRA
Previously '06 Itasca Sunrise 35A on a W22 Workhorse
'12 Jeep Wrangler Sport and/or '08 Honda Goldwing