There are four tiles in Knock Code security. To unlock your phone, you need to knock the right combination of the tiles.
Check the author's video for demonstration:
Now, to get the Knock Code on your device, you have to be rooted and have Xposed Framework installed. (Yes, this is an xposed module. For more info about Xposed Framework + download, please click HERE).
After installing and enabling the module, you should have your Knock Code installed on your device.
If you install Xposed Framework for the first time, nandroid backup is suggested.