The best of both....seal BOTh sides. This will not only seal the gap but it makes it SO easy to keep the gap clean. Sparay and wipe. I cut a pc. of covering to match the model about 1/2" or so wide, fold it in half by taking about 4"-6" length at a time, crease it by dragging it over the edge of my work bench until I have done the entire length. I then deflect the surface fully open, lay it in place, and take a 6" long thin metal straight edge and lay it in the covering groove as I slowly iron one side; come back and do the other side...fool proof !