Canon EOS-1D X Mark III DSLR Camera (Body Only) - Manual (Page 84)

< >: Multi-Function Lock
With [ 6 : Multi function lock ] configured ( ) and the power switch set to < >,
you can prevent the settings from being changed by accidentally touching the Main dial,
Quick control dial, Multi-controller, smart controller, or touch-screen panel.
Note
Attempting to use any locked camera controls when the power switch is set to
<
> will cause < > to appear in the viewfinder and on the top LCD panel
and [ ] on the Quick Control screen ( ).
By default, the < > dial is locked when the power switch is set to < >.
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