Regarding your Oct. 10 story on the fifth-wheel theft-reducing device for shopping carts:
In larger stores, collecting carts is often a macho trip for stock boys. Stock boys like to move the maximum number of carts into the store in a single trip. I don't know the record for a single string of shopping carts, but I have seen one person try to control a stack of carts that reached at least 30 feet.
The technique used to steer this string of carts is simple. With rope tied to the front cart, the pusher can bend the cart string enough to provide a modest amount of steering control.
But imagine the stock boy and his string of carts as he aims for the front door. As the front cart gets to the front door, there is often a threshold plate that provides resistance, requiring the castered wheels to be lifted slightly. With this marvelous fifth-wheel theft-deterrent, we can see the string of carts suddenly swing out of control because the front cart was lifted a little too high.