Public Displays of Affection
NO PDA!
As one of my RA's notably put it (I later borrowed from him when I became an RA), "All clothing should remain in place. And it's no excuse if s/he shows up naked."
LAN: Brief hugging is acceptable, leading to the well-circulated joke "10 seconds and you're pregnant!" Three-second close-mouth kissing is also acceptable.
The rule is possibly the result of arguably over-the-top behavior at Lancaster in 1985, but may have evolved independently at multiple sites over time.
In 2001, a list of "Don'ts" featured "No guys on girl halls or girls on guy halls". Seizing on the double negative, students claimed that this rule would be violated if there was a guys hall that didn't have a girl on it or a girls hall that didn't have a guy on it. The wording of this rule was soon changed.
In 2004, RAs began a serious PDA crackdown, especially at the dances, repeatedly separating slow-dancers and grinders of any sex combination.
LOS: As of 2004, there was no intertwining of anyone's legs. Technically, that was breaking rules. Also - holding hands was okay. Pecks were okay. Pecks on the mouth could not last longer than half a second. No making out. Hands must stay in "appropriate" places (this includes not grabbing asses while dancing). Freaking was not okay. Same sex grinding was fine. I saw most of these rules broken in session 2.
Also, these rules were not so well enforced, considering most of the RAs proceeded to break them all themselves.