Some minilabs have trays that move down; as the prints are made they are ejected from the machine; then a conveyor belt moves the prints sideways towards the tray, depositing them onto it. As soon as the tray has all the prints it needs it moves down and then an empty one drops on top of it, and the process repeats. This can be used to categorize prints, so that all prints belonging to an order are together. Other minilabs may use other mechanisms to categorize prints. This mechanism is called a sorter. Each tray has all the contents of a single order.