Two robotic arms in shuttle?

The other day when Megan (and sometimes Scooter) were controlling the
robotic arm to support the astronauts working on Hubble, the arm was on
the starboard side of the shuttle. The cameras also showed another arm
stowed on the port side.

Were there two arms on the shuttle? Or was the other port "arm"
actually a boom for the hull inspections? I thought I saw Canada
written on it too so wasn't sure.