The Mark IV Tractor Web was a device used for the transfer of cargo to and from a freighter hold in zero-g conditions. The Mark IV employed a network of tractor beam projectors around the cargo bay's opening and along one bulkhead, by which crates were moved, and though which feedback circuits were able to determine the mass.
Following the Talin IV disaster, James T. Kirk was able to take a job operating the Mark IV Tractor Web aboard the SS Ian Shelton. He noted that the device was practically identical to the cargo mover he had operated during his first six months aboard the USS Farragut. (TOS novel: Prime Directive)