How do I turn the screen on and off on my LG G2 handset?
• Double tapping(knocking) at the screen center turns on or off the screen.
(On LG Home and Lock screens, tapping at the empty zone turns off the screens.)
• When the Proximity Sensor is blocked by a sticker, film and / or case, you may find that it does not function normally.
• Tap at the center of the mobile phone. Tapping at the top or bottom may not work.
• The sensor may need correcting on the handset if you find the recognition is low.(Settings → Gesture → Correct Motion Sensor)
• How to set: App → Settings → General → Gesture → Knock On (Screen On/Off)