Just a quick note to share something I learned tonight that I don't believe was previously known. I had a meeting with ILM VFX supervisor Bill George (designer of the Excelsior and the Klingon Bird or Prey, amongst others), and in his house he had a whole bunch of scratchbuilt models he'd made of various Star Trek small utility craft all in the same scale. Well, one of those was one of the small shuttle-like vehicles seen in TSFS in spacedock and in TVH over San Francisco Bay and also in spacedock. I asked if I could see the model and he plunked it into my hands. When I mentioned that I'd never seen much on this craft, he said, "It's a tug. That's the tractor beam emitter," and pointed to the array of quarter-circle ribs on the back of the ship above the the nacelles. He went on to explain his idea that these ships would act as tugboats in spacedock, which is why you see them moving around the Enterprise...ready to guide her if necessary.
So, there ya go...right from the designer's mouth, a bit of trivia I suspect none of us knew.
You can see the tractor beam detail in the photo in row3, columns 2 and 3, and row 4, column 3 of this page.