Check out my Vanagon web site.  I have a awning rail with photos.  I use
mine with a tarp and a rope sewn into one side.  The rope and tarp slide
into this rail.

My site is at:
http://kokopellisGarden.com/vw/

>From there click on Other modifications I've Made,

then click on Awning Installation.

I hope this helps.   I riveted mine into the rain gutter.  It has worked
well even in very high winds at Burningman last year.

Have fun,
Ken