Knock ON is a function of the PHONE, as the screen is off when you try to turn the phone on with knocks (so launcher is irrelevant). Knock OFF, on the other hand, does not work right out of the box with a launcher (i.e. knock in a blank space to turn device off), because what LOOKS blank to you and I really is not blank to the phone. That blank spot is skinned by the launcher but as far as the device is concerned, it isn't blank (that's why knocking on the notification bar works).

With Nova Launcher (Prime), when you have the paid version, it enables Gestures. You can set a gesture (double knock) to launch an application. Install the free Screen Off and Lock app from the play store and have Nova launch that app when you knock twice. This gives you the same effect as knock off with the native launcher / home screen.

https://play.google.com/store/apps/details?id=com.katecca.screenofflock

Disclaimer: works as described above on G2 but not sure about the G3 because I do not have one yet.

 

When you use a different launcher, the only place you can tap on the screen to knock-off and turn off the screen is the notifcation panel. So in Nova, double-tap on top of the Battery/Network signal icons and it will turn the screen off.

Knock-on should still work unless you have replaced your lock screen with one from the Play Store.

 

^ Yep, it's what I use for my G2. Double tap is set up to launch the camera. But knock-on works just fine.

 

There may be an app/widget in the GOOGLE PLAY STORE to simulate knock-on/off:

One cool feature of OPPO's COLOR O/S (FIND 7/N1/1+1 CHINESE VARIANT) is an app that does nothing more than turn the screen off.

Just place the shortcut on your desktop & a single tap turned off the screen.

Perhaps a developer out there somewhere has pulled this & put a similar functional app in the play store,it's worth a look...........

 

Like this?
I use the invisible widget for it