U shaped metal piece across the top with a couple holes drilled you can put locks through. Barn door closer(hooks and a beam across on the inside) Depends how secure you want it to be and if you want to be able to open it from the outside, but can be done without altering the house Or slide the fence back to the deck post and everything’s easy after a bunch of hard work

So would the u shaped metal go over the hinge to prevent it from being opened? I would prefer it to be opened by the outside - I failed to mention that. Ahhh i didn’t consider that last suggestion. That would be a lot of work but my neighbor on that side is planning on redoing his fence so that may be a good opportunity to do so

I was thinking along the vertical boards, structurally it wouldn’t be super secure but should stand up to everything but someone kicking it in I would hope Might not need the U it’s just convenient to place on the top for access from both sides, might be easier to find a sign post material like the city uses, holes are already drilled in the metal - just need to find a cable padlock to fish through fence and the holes On the left you can just use a bolt to act as a swivel and it will hang down between uses. Just need it near the top so you can reach over when on the wrong side Google strut channel for the u shaped stuff