Once upon a time there were two boys and a girl. The intention was to fuck themselves silly. Running to the bedroom, they threw off their clothing in preparation for leaping onto the bed and getting wild and nasty.
Then one of the boys saw something that horrified him. He saw the other boy's cock. It occured to him that there were two cocks and one girl. It was arguably possible that at some point in time the other boy's cock could come into contact with his body, or worst, his own personal cock.
An intense negotiation broke out. The debate between the two boys carried on through such topics as how close was too close, what to do in case of an accidental cock brushing, where to dispose of cum, who gets what hole and when, how to decide when to switch positions, and how to carry out a position switch. It was of the utmost importance to keep cocks to themselves or the girl.
Speaking of the girl, she'd gotten up, went to the kitchen, made a turkey sandwich, and was watching An Affair to Remember.