CMUs existed during the mid 23rd century, often assigned to Starfleet shipyards in orbit of Earth. They assisted in the refitting of the original USS Enterprise at the San Francisco Fleet Yards as well as the launch of the USS Enterprise-B. (Star Trek: The Motion Picture; Star Trek Generations)
CMUs continued to be used into the 24th century and were numerous at Utopia Planitia Fleet Yards and Deep Space 9. (VOY: "Relativity") The CMUs at DS9 were generally gray in color. (Star Trek: Deep Space Nine season 4 credits)
The CMU was a single-occupant vehicle with seating for the pilot only. Generally, the pilot needed to be spacesuited, especially if the pilot was planning to perform a space walk. The front of the CMU featured several large windows. The craft also had a large headlight at its extreme forward end for illuminating a work area.
As the CMU was primarily a maintenance craft, it could be equipped with a variety of tools, including a set of dual remote manipulator arms called the Grabber Sled. The CMU could also serve as a tug for cargo modules with the Cargo-Train Attachment. (citation needed • edit)
- Star Trek films:
- TNG: "Coming of Age" (display only)
- DS9: (opening sequence Season 4-7)
- VOY: "Relativity"
- LD: "Veritas"
The Cargo Management Unit was never identified by name in dialogue; the name was only seen on a display in the Star Trek: The Next Generation episode "Coming of Age". During the absence of a name, the moniker "Work Bee" was adopted by many publications, official and unofficial, including the reference work Star Trek: The Motion Picture Blueprints, co-created by Andrew Probert and David A. Kimble.
The CMU was designed by Probert for Star Trek: The Motion Picture. He later remarked, "The work bee turned out just fine."  The studio model of the CMU was filmed in the summer of 1978, on one of Douglas Trumbull's stages at Future General Corporation. (The Making of Star Trek: The Motion Picture, p. 206)
Despite being proud of the CMU's design, Probert also felt that, in The Motion Picture, not enough articulation was shown in the craft. For instance, he believed that "it would have been fun" to see the CMUs enter a garage area that was included in the film's drydock. "There were supposed to have been numerous Bees, doing whatever tasks with their manipulator arms, or towing things, or whatever, and they didn't show enough of that," Probert commented. "And [...] I would have liked to have seen them drifting, or moving, or gliding/crabbing sideways through space, or rotating. They do have one that kind of rolls... but there should have been a lot more of that."  An unused design for the Enterprise cargo/shuttlebay showed several docking ports where CMUs could attach to the ship, which were described in Mr. Scott's Guide to the Enterprise.
The CMU was additionally seen in footage recycled in Star Trek II: The Wrath of Khan and during the Enterprise-B launch in Star Trek Generations. The craft was physically brought to the 24th century when it was included in a montage of different scenes during the main titles of Star Trek: Deep Space Nine, beginning with that series' fourth season. These scenes were also used for external shots of the station in various episodes. A computer-generated model was also created, and seen at Utopia Planitia during the flashbacks to the USS Voyager's launch during "Relativity".
Probert designed a follow-up craft to the CMU, dubbed the Sphinx Workpod, during the first season of Star Trek: The Next Generation. Although it was never built as a miniature or explicitly seen, it may have been included in the matte painting of Starbase 74 in "11001001". The new workpod was also featured in the Star Trek: The Next Generation Technical Manual and Star Trek: Starship Creator.
In Star Trek: The Experience's Borg Invasion 4D exhibit, Sphinx Workpods can clearly be seen repairing Copernicus Station after its brief encounter with a Borg cube. It remains the most visible and intricate use of this design.