His and hers door knockers, Yazd, Iran. The masculine door knocker is rigid and heavy that makes a strong sound. People inside the house wil be informed that a man is behind the door. The feminine door knocker is curly and ring like and makes a lighter sound. It informs the people inside the house that a woman is behind the door. This system is in place due to the Islamic custom that women should be private from men except their intimate ones.