Ditto on Caguy's post.... the hasp part is fixed to the top board. I have a padlock on mine... incase I lose the key I can use the marina's big ass bolt cutter to remove it without damaging the precious hatchboard.
In some instances you might feel the need to lock yourself in... or lock the board in place so they won't fall out in rough weather... so one solution is a series of sliding bolt latches... for the top sliding hatch, and for each hatch board.. If I were going offshore I would want to be able to lock the hatchboards in case of a knockdown......