a limited number of openings in each house, and it is impossible to simultaneously meet the preferences of all of the freshmen and houses. Despite the constraints, this two-way selection process of joining a house, and social interaction after joining, gives each house a distinctive personality that is stable over decades. Later membership There is a second way to obtain membership in a house: to apply at some point after rotation. The process varies from house to house, but in general one makes an announcement at dinner to the effect of "I would like to be a member of Booty House," and the House conducts a vote (the nature of the vote, again, varying). ("Booty House" is commonly used to refer to any unspecified house, and appears as the house named in examples of Rotation rules violations.) All houses except Ricketts have two tiers of memberships: Full members and social members. Anyone who rotates into a house is automatically a full member; individuals who would like to become members afterward can choose between full and social membership. The relative difficulties in attaining full and social memberships differ from house to house, as do the relative privileges that each membership type affords. The only universal truths are that full membership is harder to attain than social and that full members may live in house-associated property while social members may not. Generally speaking, social members are able to attend all house social events (ski trips, hikes, etc.). List of the houses South houses The south house complex opened in 1931. Blacker House Blacker House was built with the help of funds donated by Robert Roe Blacker, a trustee of Caltech. Members of Blacker House are referred to as Moles. One of the traditions of Blacker House is the hellride. In a defiant response to the prohibition against playing Ride of the Valkyries, the freshmen living in a part of the house named Hell (so called for its unbearable heat in the summer and cramped quarters) would announce a hellride. They then barricade the hallway and play the "Ride" at high volume, daring the upperclassmen to break in and drag everyone to be drenched in the showers. Blacker House features halls painted as Heaven and Hell, as well as a small lounge and kitchenette in between them known as Purgatory. Blacker's courtyard formerly featured a habitable treehouse and a giant tire swing, but