From memory the end cap is fastened on the the caravan body with just one or two screws, I can see one of them in your photo. There may well be a little plastic cap that fits over the head to conceal it. I don't think anything needs sealing.
Dave.
------------- Never argue with an idiot, they will drag you down to their level and beat you on experience.
Mark Twain.
A day of all things motorhome and campervan. The show is held both in the main indoor arena and across the grounds. Catering, hot drinks and food options are available. Easy access to the site and free parking included. Win one of five pairs of day tickets