Amazon Locker is a self-service package delivery service offered by online retailer Amazon. Amazon customers can select any Locker location as their delivery address and retrieve their orders at that location by entering a unique pick-up code on the Locker touch screen. However, certain third-party sellers on Amazon may not be able to ship to an Amazon Locker, due to their use of other shipping services such as FedEx or UPS that require a signature. There are several sizes, but when ordering, amazon.com reports some parcels are too big to be delivered to a locker.