Jefferies tube

Jefferies tubes, in the Star Trek fictional universe, are small tunnels or corridors that provide access to critical ship systems. They can be vertically or horizontally oriented, and sometimes form a network that allows travel throughout large volumes of a ship.

The term "Jefferies tube" was originally a private gag among the original Star Trek production staff, a reference to Original Series art director Matt Jefferies[?], the man who designed the original starship Enterprise. The term quickly caught on among fans, becoming an official part of the show's lexicon, and has begun being used informally in some real-world situations to refer to similar access passages.