Molding Around Everything Outside

For lights, doors, windows, hatches you use butyl rubber rope caulking which can be bought at most any RV dealer. Kind of a grey looking putty which is a rope form. It is very sticky and comes rolled with a release paper backing.

The very best way is to remove the window frame/door frame/hatch, from the trailer.

Then you can scrape off the old caulk clean with mineral spirits then put new caulking rope around the perimeter. Then reinstall the item..

REMOVING THE OLD CAULK IS the only way to do it, plastering new caulk around the outside edges only makes you feel good and wastes your money AND the life of the RV..

Thanks all, now I know what to look for at the RV store.
As for removing the windows, frames and hatches, it not something I thought would be required but does sound like the best way to go. Now long does the new caulking last? Our old 1992 Holiday Ramber (new when we bought it) the caulking lasted for the four years we owned the trailer.