1/8 x 1/16" Neodymium Disc Magnets, 4

You won't beleive the pull of these little magnets. More and more ARF's use these on battery hatches and just recently on cowlings. On the cowlings they use a keyhole slot over a screwhead, then a slight rotation of the cowl to the magnets position- locked! Think of screwing on a jar lid, but you only turn it a few degrees of rotation. Check the local electronics shack for a larger version of these, about 1.5"x 3/4" rectangles. You can actually pinch your fingers when two of these get near each other and snap together with some force. These tiny ones have no problem holding a hatch in place.