I’ve always thought that shopping cart coin locks were a fascinating innovation. Firstly, the design is very intuitive, and it’s easy to figure out how the lock system works. There’s no confusion about that, especially in models that show a picture of a quarter or a loonie on the lock. Secondly, the shopping cart coin lock is desirable, for this encourages customers to return the shopping cart to the designated parking areas to retrieve their coins, reducing employee resources and ultimately expenses required to gather unreturned carts, and also lowers the likelihood of stolen carts. Simple but effective.