For example, if someone lives in a bad neighborhood, you can use 'care of' on the envelope and send it to another address to ensure it's not stolen or tossed aside.

Include 'care of' before their friend's name and make sure you also invite their friend out of courtesy.

Sending mail to their friend: When you want to invite someone to an event but you don't know their address, you can send an invite intended for them to their friend's primary address.Sending mail to their hotel: If you need to send correspondence to someone at a hotel, but you don't know their room number, use 'care of' before the name of the hotel so they can deliver the letter or package to them.Sending mail to their workplace: If you don't know someone's home address, you can send correspondence to their workplace using 'care of' before the company's name.