The old style Tesco trolleys used to have a flat meshed bottom, below the basket at the same level as the castors. When I was younger, I acquired a couple, cut the baskets off, and welded the bottom.They made great skates to put gearboxes and such like on so you could wheel them around the garage. I am probably partly responsible for why these guys now prevent their trolleys being taken off the premesis. And they've changed the design. Spoil sports.
Martin