I use 1" wide weather stripping foam, cut into 1" square blocks. Peel and stick several squares together to get to the required depth you think would work. Finally peel and stick to somewhere the top glass and the bottom tailgate meet. I peel and stick mine to the top glass on the bottom passenger side corner, so that it contacts the interior light switch. Kills two birds with one stone. Keeps the light from blinking and stops the rattling.