Canon EOS-1D X Mark III Advanced User's Manual page 864

: Direct AF Point Selection
During metering, you can select an AF point directly with the <
pressing the < > button.
* 4: To set the direction for switching AF points with the <
the Quick control dial setting screen is displayed. [Horizontal] and [Vertical] settings for
[Direction: AF point switching] apply to Spot AF, 1-point AF, Expand AF area: (manual
selection), and Expand AF area: Surround, and [Cycle through the zones], [Horizontal], and
[Vertical] settings for [Direction: Zone AF frame switch] apply to Zone AF.
* 5: To select AF point switching ([Switch to center AF point] or [Switch to registered AF point])
when you press the center of <
screen is displayed. For instructions on registering AF points, see
>, press the < > button when the Multi-controller setting
864
> or <
> dial, press the <
Registering the AF
> dial without
> button when
Point.