Hats should be taken off indoors as a demonstration of respect, according to Emily Post. Although hats are no longer worn to define social standing, it is still considered disrespectful to wear a hat at any of several indoor occasions.
Originally, hat rules applied to men only. Women were unrestricted with regards to when and where they wore hats, but with the advent of casual, unisex hats, the rules of politeness have extended to both men and women. Hats should be removed in church, at the movies, in restaurants and in private homes. Hats should also be taken off during the playing of the national anthem and in the presence of the American flag.