Rotation Lock on an iPhone
To lock the screen rotation on an iPhone:
1.Turn on and unlock the iPhone.
2.Turn the phone round so it’s in the orientation you want to use.
3.Press twice quickly on the Home button. A strip of icons appears across the bottom of the screen. This is the multitasking interface that lets you quickly switch between apps.
4.Slide the strip of icons to the right until it goes no further. The icon at the extreme left shows a curly arrow, as in my screenshot. That’s the Rotation Lock icon.
5.Tap once on the Rotation Lock icon. A padlock is displayed inside it.
6.Press once on the Home button to get back to the Home Screen.