@merchant67 Second landplat’s suggestion of rare earth magnets. I use them all the time. I mount one under the removeable deck section & another magnet is attached to a deck framing member. Be sure to get the polarity of the second magnet correct. Two RE magnets create a strong clamping force.

No this is for the Deans Marine model Narvik which I am currently working on!!

@merchant67

Is this question in reference to the tugboat you are working on currently?

Curtain hooks and eyes, attached inside the hull stretching across the aperture, then hooked onto a curtain eye attatched to the removable hatch
located with the aid of a Button Hook or such like.. Regards Muddy.

… rare earth magnets; small and powerful…

Drill a hole and pop them in…