Yes, I always carry a bottle of water and a chain with me; along with a few other things.
A bottle jack, 2 X 6 blocks of wood for blocking, gloves, bungee cords, jumper cables, star wrench and trailer hitch ball assortment. All these go in my milk crate which is attached to the back corner by a bungee cord. I don’t go anywhere without this crate.
Most pickups have these ledges molded into the bed at the factory. These are perfect to lay a 2” X 6” board into for what ever you want to put on top of them. In my old pickup I have four on each side.
I took a 2 X 6 and cut it to fit from side to side then added a 1 X 6 to the back side. With barn door hinges I added a 1 X 8 and with more regular door hinges I added a 1 X 4. In this picture the 1 X 4 is turned under. Notice that the two boards fit between the fenders with a little clearance.
Next I took another 2x6 and cut it to fit and added a couple of blocks to get enough height to clear my milk crate. Remember I don’t go anywhere without my milk crate and bottle of water.
I thought it would be nice to have a shelf so I took a piece of ¼” plywood and added a few cleats to the underside of it and it became my shelf.
Turned over the cleats and edge board surrounds the second 2x6 that I put in. The front of the self lays on the first 2x6.
Everyone that sees this is amazed with it. I centered the shelf for the pictures but, if I have something that might slip off the edge, I slide the shelf over to one side and put a board that I cut to fit so nothing can fall off the shelf.
So now when I go get groceries or hardware they don’t wind up in the front of the truck bed.
[Sorry I don't know how to put the pictures in between the text, but I'm willing to learn.]