When guys are having sex with
girls on bunk beds, when one
guy gets tired of humping, the other takes over and his humping
motion rocks the bunk beds so the other guy can keep it going with his girl while regaining his stamina.
guy 1: "Yo bro bunk
bed sex is the best cuz when i get tired, you can
fuck your girl and rock the beds for me so i can take a break while still getting off."
guy
2: "What!?!?"
guy 3: "Yea man you gotta ride the train at least once in your life"
guy 1: "thank you!!! thats what im talking about!!"