Oh. Now I see.

The wire frame fits into the channel along the bottom of the metal frame. The ends of the wires are anchored into a hole (or holes, I forget and I don't want to go dig it out of the shed).

But, the wire frame is supposed to be sewn into the vinyl. It was a hell-for-strong seam, lapped over and double stitched. But, on mine, the thread rotted and the wire frame pulled out of it. You have the same problem.

You need to take it apart and arrest that rust. Then find the source of the leak that caused the rust. Is the windshield gasket leaking?

Then, the vinyl has to be replaced; it is most likely too degraded to accept thread.

I haven't repaired mine yet because I found another for reasonable money. I think that when I do repair it, I will use hot glue to make the pocket for the wire frame -- rather than sew it up.

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Mr. Shannon DeWolfe -- I've taken to using mister because my name misleads folks on the WWW. I am a 53 year old fat man. ;-)