ZH-28 guards were manufactured by Stonewall Labs prior to the Battle of Yavin. When the Stonewall Labs facility on Naboo was closed, security droids remained activated. Several ZH-28 guards, SWL-5 overseers, LC-92 antagonists, Mechthorians and B1-Series battle droids continued their patrol programs in the laboratory and in the surrounding area. In 1 ABY, a spacer was trying to acquire an experimental Old Republic droid module from a droideka in the Stonewall Labs facility. The spacer entered the laboratory and fought several ZH-28 guards to finally access the module.
The ZH-28 guards appeared in the 2003 video game Star Wars Galaxies, a massively multiplayer online roleplaying game developed by Sony Online Entertainment and published by LucasArts, prior to its closure on December 15, 2011. The ZH-28 guards were added to the game as part of the "Legacy Quest" with the release of the "Publish 25," a.k.a. the "New Game Enhancements," on November 15, 2005.
They shared the same model with the CY-M Prototypes and the Chirq Council Mechanized Guardians.