HTC One M8 | Lock or Off Screen with Tap \ Knock \ 3 Fingers

sources:
http://htc-one.wonderhowto.com/how-to/lock-screen-using-three-finger-tap-your-htc-one-m8-0154990/

sources:http://htc-one.wonderhowto.com/how-to/enable-unknown-sources-your-htc-one-install-apps-not-found-google-play-0151137/

1. Open your the Settings app on your HTC One.
2. Tap the Security section in settings.
3. Tap the check box next to Unknown Sources.

Step 1: Install HTC Gesture Listener

Just like most mods, this one cannot be downloaded from Google Play. Instead, make sure to have Unknown sources enabled, then download and install the HTC Gesture Listener app using this link.

Step 2: Make It a Device Admin

There's not much to actually settings up this mod. Just open the HTC Gesture Listener app, tap the Enable Device Admin button, and Activate it.

There is no need to restart your device after it installs.

Step 3: Tap Your Screen Off

Try it out by tapping anywhere on your screen with three fingers. Check out the video above for a demo. MohammadAG says that he plans on making more mods for this gesture listener, so be sure to check back every once in a while to check his progress.