The gap between the Rambox and the tailgate, which is about an inch or so. It allows water to get into the bed of the truck even with a tonneau on the truck. I've also had pollen, leaves, and flower petals getting into my truck bed even though there is a tonneau. I've been testing out a couple of different sealing methods to find something to water-proof those gaps.
What’s the best gap-filler you’ve found so far? I’d like to fill this gap as well... or at lest 90% fill it. Something better than a gaping hole would be great