A modular shelter was a type of temporary pre-fabricated field accommodation suitable for use on M-class worlds.
In 2372, when Captain Kathryn Janeway and Commander Chakotay were left behind on New Earth due to a virus, the USS Voyager beamed down a modular shelter in disassembled state. Its components came in two colors, beige and grey; since the pieces could be assembled in any order, they decided to have the grey outside and the beige inside. Chakotay noted that Janeway resisted any attempt he made to make the shelter more of a home. She explained that it felt like he was giving up on returning to Voyager. Later, he suggested adding rooms to the shelter with wooden logs sourced from the planet. (VOY: "Resolutions")