[Rixson]

I would contact Zip Dee . They can make a new replacement fabric .
847-437-0980

Thank you for sharing the number.

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The narrow white fabric is a piece Zipdee refers to as a KEY. It can be made from Sunbrella fabric by any awning shop. Same thing for the awning. Suggest you look at Sunbrella fabric on the Sailrite website. Many years ago I bought the replacement fabric AND a walking foot sewing machine for way less than Zipdee wanted for replacement fabric. That may not be your forte, just saying. Otherwise find an awing shop. They can make a new key, and restitch the separating fabric on the main awning.

The channels that the key slides into are crimped on the ends and in several places in the middle. You MUST uncrimp the crimps or the material WILL NOT slide out. I found a pair of vise grip pliers to be the best tool for grabbing the channel and bending it open.

Oh yeah, Ms Beaty my high school English teacher would congratulate you on knowing how to spell separate. I will never forget her saying it has a rat in it.

This is incredibly good information. Thank you !!!   As usual, Guru Richard, on top of the details. 
I was surprised that the key parts were only in certain places in the slide, as opposed to all the way through the slide, but then I guess friction over 20 ft, it makes some sense.
I'm gonna bet Ms Beaty is part of why you're an amazing individual and so helpful.    

Thank You