Real World article
(written from a Production point of view)
ODN junction box

An example of a Mees panel

Mees panel was the behind-the-scenes nickname for the various service panels and junction boxes seen aboard the starship USS Enterprise-D throughout the run of Star Trek: The Next Generation.

First coined in the script for the sixth season episode "Aquiel", Mees panel refers to TNG (and later Star Trek: Voyager and Star Trek: Enterprise) set decorator Jim Mees, much in same way Jefferies tube and okudagram refer to Matt Jefferies and Michael Okuda, respectively.

Used as script notes and never spoken in dialogue, Mees panels appeared whenever characters were required to access the internal circuitry of the Enterprise – each panel designed and built at great expense (around US$1,000) by Jim Mees and the Star Trek art department. According to Larry Nemecek's Star Trek: The Next Generation Companion, writer Ronald D. Moore was infamous for using the panels, despite the fact that the sets of the Enterprise-D did not already include accessible panels the way a "real" starship would.