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LG G3 D851 Knock ON™ & Knock Code™

Operation Cell Phones Last Updated 12/12/2018
>LG G3 D851 Knock ON™ & Knock Code™

With Knock ON you can turn the screen on by quickly double-tapping the screen. Double-tap an empty area in the Home screen, Status Bar, or Lock screen to turn the screen off.

Knock Code is a security feature that enables a user to unlock the phone when the screen is off. The Home screen can be accessed directly if you tap the sequence anywhere on the screen.

Knock ON and Knock Code can be used simultaneously.

Note: Knock ON feature cannot be disabled.

See the Lock screen article for additional information on setting up your lock screen.

A quick double-tapping on the center of the screen turns the screen on without pressing the Power/lock key. The phone senses the gesture and turns the display on or off.

image of double tap to wake

Note: The Knock ON double-tap wakes the display. If the screen lock is set to None, Knock ON will wake to the Home screen; otherwise you will see the lock screen (Knock Code shown above).


  1. To reduce battery consumption and prevent unintended knocks, G3 is designed to sense the knocking gesture anywhere on the screen, but preferably in the area on the center of the screen.

  2. If the phone is moved when you knock on the screen, the knocking gesture might not be sensed. e.g. Knocking the screen with your thumb while holding the phone in your hand.

  3. You should double-tap with a fingertip, not with a nail, to wake the display or put it to sleep.

  4. Knock On feature cannot be disabled.

  5. You can use your Google Account (if setup on phone) and backup PIN in case you forget your knock code sequence.

  1. From the Home screen, tap Apps  icon > Settings  icon > Display tab > Lock screen  icon

  2. Tap Select screen lock > Knock Code.

  3. Read the tutorial and tap the Next button.

  4. Tap 3-8 times in the 2X2 grid shown to set your knock code. Then tap the Continue button. 

  5. Re-tap your code and tap the Confirm button.  

Note: Follow the on-screen instructions to create a backup PIN number in case you forget your knock code.

Screen off

When the screen is off, holding the phone in portrait orientation, tap the sequence of your Knock Code anywhere on the screen to access the Home screen directly. You can enter your code in a small space, or over the full width of the phone..

 enter the code with the screen off

Lock screen

Use Knock ON double-tap or press the Power/lock key to wake the screen. Tap your Knock Code sequence in the area enclosed by angle brackets (as shown below) to unlock your phone .

 enter the code with the lock screen

Note: Images simulated. Actual device does not show highlighted circles when the screen is pressed.

  1. After five incorrect Knock Code attempts, a notification appears saying “Wrong Knock code entered 5 times in a row...” and a Forgot Knock code? button appears at the bottom of the screen. Read the notification, and tap OK.

    wrong knock code message

  2. The next screen shows a 2x2 grid that provides the same environment as a Knock Code setup for a more accurate input.

    forgot knock code option

  3. If you incorrectly enter your Knock code for the 6th time, you cannot enter it anymore. You should unlock your phone by logging into your Google Account (if setup on phone) or by entering the backup PIN you created during setup. Then tap OK to unlock..

If you do not have a Google account added to your device, you will need to perform a factory reset. To learn how to perform a factory reset, click here.

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