While I certainly like and agree that weatherguard and a couple other high end boxes are of superior quality my $200 (well at least at the time I bought it) Deezee box has been totally dry for the last 14 years. Even though the weather stripping is half gone around the top of the lid. Now the lid as I think all do goes over the outside edges of the box itself. It does have a few holes in the bottom of the box(it came with them and with the weather stripping messed up at this point it is far from airtight but have never seen a drop of moisture in it. It may be as mentioned previously condensation so perhaps a few holes drilled in the bottom would help alleviate it even perhaps high on the sides beneath the bed rail overhang to promote some airflow.