Beginning in 2014, LG phones function declared "Knock code". It is stated that this feature is a new and popular.
What is actually Knock code, it is just a small program that is installed on the phone manufacturer and allows unlocking the phone's screen is not just pressing the power button, and clicking on certain areas of the screen. The user sets their own sequence. Programmed areas of the screen can be from two to eight, that means to unlock the screen the user must press on the screen from 2 to 8 times.
Kinda is the installation code to prevent unauthorized use. The claim that it is more convenient than a click is debatable, it is better to click once on the button, or 8 times the screen.
And besides, graphic codes, invented a long time protective function. Only a few manufacturers such as do not divide the screen into several areas, such as output points to be connected in a certain sequence, the same code but a little differently implemented.