These are luggage lockers in Union Station in Chicago, Illinois. Placing your luggage here is like parking a car in a paid parking garage. For the largest lockers, the cost is $1.25 per hour up to a maximum of $7.50 per day. There were smaller lockers for less per hour, but I think the maximum was always $7.50 per day. You have to pay for the first hour up front and then the door opens a slip is printed with an access code. When you reclaim your luggage, you have to pay the amount owed before the door will open. There are change machines that can change $1 and $5 bills in the locker area. There is also an attendant in the locker area in case you need other help.