You shouldn't scribble on someone's personal item.
Cindy is at her boss's desk talking with someone from technical support.
Cindy wants to write down a phone number.
Cindy writes the number down on her hand, so she will remember it.
Cindy writes the number down in her boss's date book.
Cindy is able to call the number when she looks at it on her hand.
Cindy's boss yells at her because he can't see the information in his date book.