I have a 2012 Manning trailer, I see no bolts holding the bunks to the trailer. How do they attach the wood bunks to the trailer?

if you look carefully on top of the bunk you can see the small holes on the carpet were they ran the self tapping thrue

have to keep a eye on those ,was at the swimming hole one day ,wiping down the side of the boat ,holding onto the bottom I found gouges, the wood had compressed over time and the screws don't move. I replaced the bunks and used carriage bolts,so it has give