Samsung LS20HANKBHDZS - Manual (Page 25)

Locked
After pushing the "MENU" button more than 5 seconds, OSD function is
locked (unlocked).
You can adjust only the brightness and contrast of the
monitor with the OSD adjustment locking feature.
Customized key
Menu Description
Customized key
You can customize key assignment for the Custom button according to
your preferences.
To view the operating screen displayed when pressing the [ ] button
after configuring the customized key for a function, click the name of each
function.
(
Image Size - MagicBright - MagicColor - Color Effect )
You can configure the customized key for a required
function via Setup >
Customized Key
Brightness