It's no problem making gun port lids from wood using strips in two layers. You will have to make some wood strips from scrap or buy some. If you want to get super detailed, match the planking seams on each lid to the surrounding hull planking. If the lids are displayed open, you won't see if the planking doesn't line up.
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Nonfunctional hinges for the lids appear more realistic to scale. These hinges come with Corel model kits and are functional, rotating on bent brass pins normally used for holding planks to frames.
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Test fit of a gun port lid. All the gaps and misalignments in the lid and planking show up under close photography, but this ship is small at 1:100 scale, so every flaw is evident when you get this close.
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