A yard superintendent was a Starfleet official who commanded a shipyard.
Such officials made decisions about the operation of the yard, such as which starships to repair, in what order, and when they could leave.
During the Klingon Civil War, Captain Jean-Luc Picard assembled a fleet at Starbase 234 to implement a blockade of Klingon space with starships at the base. He made some starships part of his fleet, including the USS Hermes, USS Sutherland, and USS Tian An Men, despite the yard superintendent stating that they were not ready for launch. (TNG: "Redemption II")