My dad used an actual ammo box as his portable tool box.
It slid comfortably under the front seat of his car. A bit shallow for the 1/2" socket set, but the 3/8" fit just fine, along with a few combination wrenches and screwdrivers and spare parts and such. I’m more of a packrat (plus I prefer to use the bigger 1/2" drive sockets for most automotive jobs), so my car toolbox is kinda big and cumbersome by comparison.
