FOX's innovative BOC is a position-sensitive compression adjustment that only affects the last 25% of travel. This independently tuned compression adjuster uniquely protects against bottom-out events, even when your high- and low-speed adjusters are set light.
The BOC is the green adjuster next to the DSC. Turning the BOC adjuster clockwise increases bottoming resistance; counter-clockwise decreases resistance (standard setting is 12 clicks out).
The goal of the BOC is to run as little end-of-travel damping as possible to maximize wheel travel without bottoming hard.