Apple has won two US patents on the iOS folder system. The first is titled Device, method, and graphical user interface for managing folders, and specifically documents the way iOS users can create folders by tapping and holding an app icon, which triggers a "jiggle mode" that lets people rearrange apps. Dragging one app on top of another puts the two items into a new folder. Alternately, tapping X on an icon lets people remove an app from a device entirely, and icons can be dragged out of existing folders.
