>>taraka+(OP)
Years back we rented a flat in a building that housed a lot of retired people.
A regulation we weren't aware of was that you weren't allowed to hang anything on the railings of your balcony.
On a day off we were cleaning and left a mat we'd washed to dry, hanging over the railing. It wasn't there an hour before we had a delegation at our door of angry elderly residents. They weren't one bit nice about it even after we immediately apologised, took down the offending item and explained that we were unaware of the regulation.
Later we got an apologetic call from our landlord who said he was ringing because he'd received a complaint about us.