I think they call it a balancing cylinder. It's not hooked to anything, but reacts to the fluid pressure coming off the cylinders that are doing the work of moving your slides. Kinda like, for every action there is an equal and opposite reaction theory. Just what I have been told on mine.
Randy & Kathy-n-Auggie
07 HR Navigator 43PBQ, 525hp Cummins ISX, 17 Ford Supercrew Ecoboost King Ranch 4x4