What Is This Rotor Thing?
The VoiceOver rotor is perhaps the most difficult aspect of VoiceOver to get used to because it is not a concept used in other screen readers. It is basically a way to use the same two gestures--up and down swipe with one finger--to perform multiple tasks. That is, an up or down swipe will do the action set in the rotor, and the rotor can be set at any point. The rotor is commonly used for reviewing text by word or character, changing the typing mode, and editing text. It can be used to move by many different elements, such as link, heading, form control, and the like. At any point, the rotor options will only be those that are valid for the current context. For instance, many web pages will allow navigation by heading, link, landmark, and more, while a page in settings may offer only headings. Character and word navigation are always offered, as are any options you enable in VoiceOver's rotor settings.
To change the rotor setting, place two fingers on the screen and turn them. The important thing is that each finger moves in the opposite direction as the other finger, but at the same time. This means that, if you are having trouble "turning the rotor" with one hand, you can use one finger from each hand and move them in opposite directions. You will know when you are successful when you hear a scratching sound and VoiceOver announces the new rotor setting.
Once you have moved to the desired setting, swipe up or down with one finger to perform the selected action. This is where things can get confusing. When set to most settings, this swiping motion will move by the rotor item. For instance, selecting "words" will make the upward swipe move back one word, and the downward swipe move forward a word, in whatever VoiceOver is focused on at the time (the name of an app, a button, or anything it has just said). Some rotor items, though, are menus of options. These items include edit and typing mode, both only available when you are editing a text field, or the actions available on some elements such as emails. Swiping up or down will, instead of moving by any amount through the text of what you are focused on, move up or down one item in the menu. When you hear the item you want, double tap.
Finally, the up and down flicking gestures are also used to control things like table indexes or sliders. When you are on such an element--such as the volume control in the Music app or the Speech Rate adjuster in VoiceOver's settings--swiping will move by a certain amount, normally ten percent. You will also find that a new item appears in the rotor, called "adjust value". When you are on an element that requires the use of the up/down swipe, this rotor item is selected automatically. Once you leave the adjustable element, your previous rotor setting is selected and the "adjust value" item disappears.
Sometimes, you will hear the scratching sound that indicates the rotor has turned, but the setting will not change. In this case, just repeat the turning gesture, moving your fingers a bit more than your previous try. In addition, rotor items may seem to be skipped. This just means you turned the rotor a bit too enthusiastically and moved by two rotor items instead of one.