Torn Shade on Graphic Back

One of the cloth shades on my graphic back ground glass cover has been pulled out of the lip on the edge that holds it in place. I tried to take a very small screw driver and lift up on the lip to slide it back in place, but not even a razor blade will fit under there. Does it come apart a different way and then gets tightened back when the cloth is in place? I can't seem to get it back under there.

I've managed to repair two, but it's difficult to open the gap, I used a vice and 2 bits of wood to press the lip back closed.

Ian

Can you post a photograph of the problem?

Steve