I used to use it for an old iPhone with a broken button to turn the screen off. However I have finally delved into the 1200 page iOS 11 manual to discover some more subtle uses for my newish SE and it has finally solved a couple of irritating actions that are now easy. This is what I use it for. Rotation lock is something that I'm often faffing around with and that necessitates a trip to the control centre and then a scan for the right button. The other thing is that I find using the power button to lock the screen annoying too. So I use assistive touch button for both with Custom Actions... First I add the button then I reduce its Idle Opacity to the minimum I can which is 15% Then I have in the 'custom actions' a single tap set to Lock Rotation Lastly I set the Long Press to Lock Screen and the Long Press Duration to 0.25 seconds Anyone else love this button.