Orangeleader is correct looking at the picture you attached. If it doesn't work to hook the bottom hook of the pannier to the junction of the 3 tubes in the rack I would suggest buying a small hose clamp that would fit around the rear tube of the rack (the one that slopes up to hold up the rear of the rack). Tighten the hoseclamp around the tube near where it joins the other tubes, with the screw on the bottom side of the tube. That will provide a stop to keep the pannier hook from sliding up the tube and coming loose.