I'm assuming that we're talking about the 3000 sheet feeder tray or a sorter that rolls on a track to left side? If so, then I can tell you from experience on 8150 printers that the arm is held in place via a plastic piece that has tabs on it. On the printer at the arm there should be some tabs that can be squeezed together to release the securing tabs. They can be difficult, so you may have to squeeze and also pry a bit underneath.
Good luck,
Mike