Vinyl insert molding trim

Make sure you're buying the right width insert.

Also make sure it's not being stretched or stressed anyplace, it seems to want to pop out if that happens. I have had to put just a small amount of silicone under it in some corners to glue it in. Don't use so much that water cant drain under it though.

A lot of trailers will have a small screw through the molding at each end and often up at the top corners to help keep it in place.
Barney

Dunno what size/type your molding is, but some such installs use endcaps. My trailer has aluminum insert-type caps at the molding ends.

Another type of cap goes over the top and fastens with a screw- see pic below. (They're available in black, too.)



link to source

As mentioned, the biggest thing to keep in mind is to not stretch it at all when installing. Any stretch will try to shrink back up and will pull out at the corners, allowing the wind to catch it and take it away.

I had to use a hair dryer to soften the vinyl to make sharp turns, then hold in place till it cools and returns to shape.

stuff it in to prevent stretching. Here in Az didn't need any more heat. Then installed screws @ the ends works great like said before it comes in 3/4 & 1" Make sure it's the correct size and just keep pushing it back towards the end you started on to prevent stretching. Good luck