Lock it if you can and be done with it.
I have one set of returning guests who go into the linen closet in the cottage, rearrange the contents and store some of their personal things in there. There is no need for this since there is another full closet just across the room. They are the only guests who mess with the closet, but they are otherwise neat and clean and very accommodating. Just the same, if I had a lock on the closet I would use it. I just don't like the idea of anyone messing with supplies..
we once had guests on the third floor who decided to store their bag in the eves. So they opened the access panel to the eves and oops, a bunch of wasps came out.
it's an old house. don't mess with the balance. and who told you you could open an access panel into my attic space? I store stuff there!
anyway, nature punished them. I didn't have to.
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I believe in locking every possible place I don't want people to go into. Theft, liability, damage, etc.
They rented the room, they have access to the common areas. Laundry, closets, kitchen, attic, basement, sheds, owner's quarters, unrented rooms, etc - all will be locked.
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