Sorry I double checked and its Keder Welt, not kelter welt and I actually used the 9/32" keder welt.
It is a very simple system, the keder-welt just slides through flex a rail (even with the screws in it) and you can sew the overhang portion of the keder welt to whatever you want, I went with a tarp as I didnt want to spend much money not knowing if it works. I imagine once the tarp gets worn I will remake it with something a little nicer. One thing I should point out is it can slide back and forth in the rail, so I use a little piece of rope at one end to secure the location of the awning in the rail when it gets a little windy.
Also because it is attached to the trailer it is not very tall, which if someone wants to stand under it they either need to be short (like my wife) or not be bothered by the height. I am 6'5 so no matter what awning I used I would have to duck.
I can take some more pictures later, but I dont keep the trailer at my house, so it wont be for a week or so. The links below should help a lot.
Here are the links to what I used:
https://www.jtsoutdoorfabrics.com/Keder-Welt--932_p_11359.html and
https://www.jtsoutdoorfabrics.com/Flex_A_Rail.
