iOS 4 allows you to lock your iPhone in portrait mode by double clicking the Home button, swiping the dock left, and clicking on the lock icon.
However, it does not appear to allow you to lock the iPhone in landscape mode, which can be desirable for some applications. Instead, the lock always seems to force portrait orientation.
How can I prevent my iPhone from rotating out of Landscape mode?
Best Answer
Orientation lock on iPhone with iOS 4 only does portrait lock at the moment. Hopefully they will have landscape lock on the next update.