The history of the quarter-moon on the door of the outhouse goes way back. Most serious historians who are students of the subject are of the opinion that the custom started in Europe in the 1500s or the 1600s. It was common practice, back then, to identify which outhouse was which by means of a circular symbol on the door of the mens' and a quarter-moon on the ladies'. The use of symbols rather than words was necessary due to the widespread illiteracy of the times. When a feller can't read and is headed for the outhouse, he sure doesn't need some incomprehensible hieroglyphics on the door to figure out. The circular symbol and the quarter-moon were Europe's version of the Chinese Yin and Yang. The circle was representative of the sun which symbolized masculinity. The more subdued and submissive moon, on the other hand, represented femininity. The use of the circle and quarter-moon was especially common at inns and houses for lodging. Not only was illiteracy a problem, but also the clientele of such places was more likely to be travelers from another country and another language. These universal signs were easy to make and easy to "read", so most such had the little houses out back so designated, one with a circular sign, and one with the quarter-moon. So why is the quarter-moon applied in more recent times to outhouses in general? The answer to that apparently lies in the economics of maintaining outhouses. If one of the outhouses at an inn, for example, were to have fallen into a state of disrepair, the solution was often to transfer, if necessary, the quarter-moon onto the surviving structure. It was reasoned that the men could always simply step into the shadows of the trees. An outhouse had to be kept for the ladies, of course, so whatever outhouse fell apart first was automatically the men's. This practice became so widespread that in many cases only a women's outhouse would be available to those who frequented such public places. Since those carried the quarter-moon, that symbol soon evolved into the sign for any outhouse, in general, rather than one for ladies only."