whoever made it did not want bait sliding overboard???
.. got tired of loosing pliers or beers overboard???
some mfg companies made "tooling" bumps, strakes, or a mold to get strength.. Id add some divinycell core with glass on top or teak it . looks like the height wouldn't hurt.
An easy way is to rip down starboard,pre drill and counter sink for screws and screw it down.I've put a bunch of them on skiffs to keep fly line on the deck.
The product is made of pvc and can be purchased through Hamilton Marine, located in Portland Maine. All shapes, styles and lenghts. They are on the web.