Canon EOS-1D X Mark III EOS-1DX Mark III Advanced User Guide - Page 385

[ 5] AF point selection movement When AF points are selected, you can set whether selection stops at the outermost AF point or continues to the first AF point on the opposite side. [ ] Stops at AF area edges Useful if you often use the outermost AF point. [ ] Continuous Instead of stopping at the outer edge, the selection of AF point continues to the opposite side. Note Also applies when the initial AF point for AI Servo AF is selected with [ Servo AF pt, / ] set to [Initial Servo AF pt, / ]. : Initial 385