 Several uncrewed spacecraft use NASA's berthing mechanism rather than a docking port.The Japanese H-II Transfer Vehicle (HTV), SpaceX Dragon, and Orbital Sciences' Cygnus spacecraft all maneuver to a close rendezvous and maintain station-keeping, allowing the ISS Canadarm2 to grapple and move the spacecraft to a berthing port on the US segment.The Russian segment only uses docking ports so it is not possible for HTV, Dragon and Cygnus to find a berth there.