I found a video describing a clever way to turn old bags into panniers
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How to make a bicycle pannier
https://youtu.be/T2s53x1K-kI?si=FltzJMh5VkwO8RW-
Description on how I made a canvas bicycle pannier for commuter bike. I wanted something I can wear over my shoulder after riding the bike.Use a bungee cord ...
I am sure this would work for messenger bags, camera bags, or really any bag. And hard board backing could be added to them from rubbing on the wheels.