Canon EOS 5D Mark III Instruction Manual (en)

Basic Operation
The <
9> consists of an eight-direction key and a button at the center.
Use it to select the AF point, correct 
the white balance, move the AF point 
or magnifying frame during Live View 
shooting, scroll around magnified 
images during playback, operate the 
Quick Control screen, etc.
You can also use it to select or set 
menu options (except [31: Erase 
] and [51: Format card]).
For menus and the Quick Control 
screen, the Multi-controller works 
only in the vertical and horizontal 
directions. It does not work in 
diagonal directions.
With [82: Multi function lock] set (p.325) and the <R> switch 
set to the right, it prevents the Main Dial, Quick Control Dial, and Multi-
controller from moving and changing a setting inadvertently.
<R> switch set to the left: 
Lock released
<R> switch set to the right: 
Lock engaged
R Multi function Lock
If the <R> switch is set to the right and you try to use one of the locked 
camera controls, <L> will be displayed in the viewfinder and on the LCD 
panel. On the shooting settings display (p.48), [LOCK] will be displayed.