How do I lock and unlock the OSD of a "AOC monitor 21'"?

According to aoc page you need to do the following for one of the displays:

OSD Lock Function: To lock the OSD, press and hold the MENUbutton while the monitor is off and then press power button to turn the monitor on. To un-lock the OSD - press and hold the MENUbutton while the monitor is off and then press power button to turn the monitor on.

If it doesn't work try searching for your display on the page. Or check the manual you got with monitor.

OSD Lock Function:

To lock the OSD-First make the Monitor off by pressing power button and then hold the Left button for 5 seconds and simultaneously hit the power button with the left button and the osd is Locked.

OSD UnLock Function:

To Un-lock the OSD - Repeat the above same Process and Then OSD is Unlocked

My one is AOC. What I did is, First turn off the power button and then press the power and menu button together, if its shows on the display the OSD lock message then it means its hasn’t worked but if not then it means it worked... I tested this myself