During the party, everyone tries to find the matching nuts and bolts. Matching pairs determine parings for whatever activities are planned for the after-party. Often it is used to detremine who is going to have some sort of sex with each other.
I got so hard watching Jill giving Bob a blow job while I was licking Suzy's pussy. I think Bob was surprised that Jill swallowed his cum. Suzy had me cum on her tits, but she gave one hell of a blow job otherwise.