They use the tiniest of holes.

We had a tile missing on our roof because the tradesman forgot to put it back.

A family of possums moved in. Bear in mind these animals are nocturnal so they would arrive 'home' at 5 am and run around in the ceiling.

What we did.

We waited until it was dark and they were out doing whatever possums do.

My husband scaled a ladder, me with torch in hand to guide him.

That got fiaed, but the next morning when the possums came 'home' all hell was let loose. We had to put up with it for a few days, after which they gave up.