On my trailer door, after a lot of struggling I found I could just reach the end fitting with the ends of two fingers, turn it through 90 degrees, and lift it out of the vertical slot. This is at one end only. The other bracket has a small hole for a pin on the end of the roller. I don't remember which end was which. It appears impossible at first, but, after learning on my trailer, I did the job in a few seconds for an Airstreamer I met last winter at Long Key State Park. Home Depot will make a replacement blind c/w roller for a few dollars. Happy struggling!
Nick Crowhurst, Excella 25 1988, Dodge Ram 2500 Cummins Diesel. England in summer, USA in winter.
"The price of freedom is eternal maintenance."