But if a family is concerned, when you're actually trick-or-treating, if you watch your child go to someone's door, ring the bell, and the other family comes to the door and hands them candy, it's one way of knowing it's a safe and comfortable gift of the candy.

CNN: Kate Kelly: Halloween safety

You waited for the door-to-door salesmen to ring your bell.

FORBES: A Foot in the Door No More

If you hear things getting violent next door, you can ring the bell or call the doorman or the cops.

CNN: To stem violence against women, men must step up