Well, I've been lazy for a while and hadn't really made a bottom /side support to my tool bag panniers. I had found a shoe box that was about the right foot print and covered it with a plastic bag and stuck it in - it worked, but it wasn't ideal. I was waiting for a rain storm to ruin my box. But I've carried groceries, a ton of library books, etc. using it with the cardboard box.

I really like the tool bags 'cause they're not so long and I don't hit them with my foot/pedal on the backstroke like I do with the other panniers I've tried.

I was going to eventually cut a piece of wood to do it... and had been debating maybe a metal support...

But the other night I was cleaning and looked at the wooden clementine box that I had on the table and had a eureka moment... I went and checked, and yeah. The clementine box was the same size as the bottom of the tool bag.

So I had to dismantle two sides of the box to get it to fit into the bottom of the bag, but now my panniers have a hard support for the back side & bottom...

Just 'cause I like posting pics of my bike, here it is on my way back from the library (tool bag was open on the way there with 8books in it, I closed it on the way back 'cause I only picked up 2 & it only had the cardboard box in it for support at that time.)