Awning rail protectors

I leave ours in (one on each side) and have never had a problem. They do slide about a bit as they're shorter than the rail but the end caps on our awning rail mean they can't fall out.

I doubt such a small surface area would have any great effect on stability.

I leave mine on as well. I found that they don't move but have put off cuts as wedges at either end just in case.

I doubt if such a small area of plastic will have any effect on such an unaerodynamic vehicle as a caravan.

Caravans have any number of protruding items, widows, doors, flaps, aerials, flues and chimneys so I really would not worry about two small (in cross section) bits of plastic.

I keep them in also-brought 2 and cut them to suit the entire length of each side rail.

Never been an issue and they are still there ;-)

Question: why do you use awning rail protectors ? 

I've never felt the need for them ...

Because they stop all the dirty water on the roof running down the side of the van and leaving black marks.

Their name is rather misleading. Water deflectors would be a better describe their function.