Hint 1: Did you open the wardrobe?
Hint 2: Archimedes' principle.
Thanks.
Ha I'd forgotten to open the wardrobe. I now have the trunk. I still feel I'm missing something, because it looks like I now need 3 keys and can't even get 1, and I think I need to get upstairs in the house but can't do that either.
By the way there's a bit of translation missing: when you have the trunk down. If you try USE HOOK ON TRUNK it answers in Czech: To neni spatny napad, ale nepujde to