How to secure a door without adding a lock?

Got myself in a bit of a situation. A family member is throwing a party at our place while I’m away, and I want to make sure my room stays secure. Problem is, the house is old, so I’m not allowed to add any locks or make modifications. The door doesn’t fit the frame perfectly but can still close. Any suggestions for securing it from the outside without screws or adhesives? I have a small round doorknob, if that helps with any ideas!

You could swap out the doorknob with one that has a key lock temporarily, then switch it back afterward.

Honestly, an angry dog might be the best deterrent here!

Consider getting a large lockable box to store anything valuable in your room.

You could install a lock temporarily and remove it when the party is over.

Check out ‘portable locks’ on Amazon. These don’t need any screws, adhesives, or modifications. But you’d need to use it from the inside, so you’d have to exit through a window. Hopefully, no one would notice the unlocked window.

Why allow a party while you’re not there? Get a footlocker to store your valuables, password-protect your computer, and keep all personal items secure. You might also consider asking them to sign an agreement covering any potential damages.