Umbilicals are corridors branching out from UNSC Orbital Defense Platforms that serve as docking points for other ships.
Cairo Station Umbilicals
During the First Battle of Earth, SPARTAN-117 cleared the portside Umbilicals enroute to the Covenant Bomb in Firing Control. This allowed Commander Miranda Keyes, Johnson, and her Flight Lieutenants to board the UNSC In Amber Clad.