Calling cards became an indispensable tool of etiquette, with sophisticated rules governing their use. The essential convention was that one person would not expect to see another person in her own home (unless invited or introduced) without first leaving his visiting card for the person at her home. Upon leaving the card, he would not expect to be admitted at first, but might receive a card at his own home in response. This would serve as a signal that a personal visit and meeting at home would not be unwelcome. On the other hand, if no card were forthcoming in return, or if a card were sent in an envelope, a personal visit was thereby discouraged.