Hi,
Here is how to really seal your locker...or any closure.
Get some GE silicone..clear ..you'll need enought to go around the perimeter of your locker cover.
open the cover ...carefully squirt a bead --3/8 inch high or so along the top edge of the locker cover and down along the sides.Just the Edge..so this is a cereful steering job..keep hands off and no need to do the bottom edge.
Get Saran wrap...or clear plastic food wrap and carefull lay along this edge enough to cover the silicone ..leave some on each side hanging down.
Now lightly pinch along the edge covered with plastic wrap...form a gasket that will be covered with the plastic so clean hands...
I try not to let any squeeze out each side of the edge...
gently lower the cover .leave it over night or so. It will conform to the cover and the opening .... peel off the plactic and you are all sealed.
Hope this helps,
Marvin Kowalewski
parker 27 #138 The Happy Seal
Marvin Kowalewski, Ph.D