When going to acquire alcohol, you inexplicably end up on the roof of the high school you previously attended. You will most likely get spotted by a security guard, but he will laugh about it without scolding you the next day. Almost always done with one purchaser of legal age and at least one underage provider of cash.
18 year old-"Hey! What are we doing on the roof of my high school?!"
21 year old-"It's a Crockett Beer Run!"