Backpack as Pannier

Hey, I already have a waterproof roll-top backpack– why not use it as a pannier?

Mandrel/anvil and heavy-duty spur grommets (with teeth).

Grommets added to the bag, rack hooks bolted to them with locknuts. I could redo this later to have the grommets set in a separate piece of sturdy webbing, which is then sewed to the bag to distribute the force.

And loaded with groceries:

(the straps are folded under the bottom of the bag and held in place with velcro, to keep them from getting sucked into the wheel)