Mounting hardware is sold for the boards or with the boards. I recommend using the ones for the boards you buy.

Completely off topic but what size is your boat hatch?
24” Vetus marine hatch.
Build thread
Marine Deck Hatch Install
I went with the 24” Vetus Magnus Marine Deck Hatch. It should be here sometime this week. https://www.defender.com/product.jsp?id=2359493 I’ll have to remove one roof rib for it to fit properly. I don’t have a garage so I’ll have to cut and install first and then support afterwards. This isnt...sprinter-source.com