PO box numbers are not just for your postman. They are used by visitors looking for your home and even by emergency services responding to an emergency call. So make sure your mailbox is clearly labeled and these numbers will do the trick really well. Installation is very easy (just peel and stick) but make sure you apply these numbers to a clean surface. A spray all-purpose cleaner and a microfiber cloth are sufficient. And note that once they get stuck, they get stuck. Uninstalling and reinstalling doesn't help. So place these numbers carefully. Measure twice and glue once.