Canon EOS-1DX Af Setting Manualbook page 97

Set up steps
First, select [Separate AF pts: Area+pt] from [Orientation
linked AF point]. Next, select the AF area selection mode
and the manually selected AF point for each of the
positions (orientation) of A) Horizontal position, B)
Vertical position with grip at the top, and if required C)
Vertical position with grip at the bottom. The settings will
automatically be remembered. Now, for each of these
orientations the camera will automatically switch to the
select mode and AF points.
97