A docking web was a device built into Leviathans that acted similar to a tractor beam. It was used to guide ships into the transport hangar. After drawing the vessel into the Leviathan, the web would guide it to a given landing area, as dictated by the Leviathan's Pilot.
When Moya first encountered Farscape-1, Pilot drew it into the ship to see if its pilot could assist them with their escape. ("Premiere")