Howard Wolowitz built and then "borrowed" this arm from the Jet Propulsion Lab, and took it home for his own uses.

It was originally destined for the International Space Station in "The Robotic Manipulation", but Howard stole it, then used it to unpack dinner, serve napkins, give massages and help him masturbate, which is when he gets it stuck and cannot de-program it because he would have to turn it on but the computer thought that it was "holding a space screwdriver." It is assumed that he returned it after the episode.