… shopping trolley.
These high-tech thingies are daisy-chained and to release one, you need a €1 coin* for the slot.
Can’t get far if you want to steal one, though. Some outfits have RFID based (I think) perimeter protection which locks the wheels when you leave the premises.
*Plastic disk works, too.
Which reminds me of when I was working in the UK and frequently in Germany and someone worked out that a 5p coin fitted the 1DM slot on cigarette vending machines.
Instant price reduction of 95%….