Wrench-bot (First proper appearance here) is an AI-equipped pipe wrench from Riff's apartment in 4U City. Due to a quirk in the virus Riff used to make him independent from 4U City's infrastructure, he gained a Cockney accent (something that often prompted Riff to order him to assume silent mode). Riff used him to make deliberately-temporary repairs to the apartment's plumbing (the purpose of these being to generate windows in which Riff could be cleansed of the city's drugs when he entered the cover of the crawlspace), and therefore Wrenchbot was, shall we say, instrumental in the revolution and Riff's eventual return.
During the descent to the lair of "His Masterness", Wrench-bot was used to ascertain the depth of a pit down which Riff and Executive Rammer had to descend(Seen here). Later, after DoR Torg failed to use him to clonk Executive Rammer over the head, he complained of a cramp in his arse (here)