"Until you pin me, George, Festivus is not over!" -Frank Costanza
In accordance with Festivus tradition, the celebration may not end until two people participate in a contest known as the Feats of Strength. During this event, the head of the household (or the host of the Festivus dinner) challenges one of the guests to a test of physical strength. The challenger may choose anyone as an opponent and a challenge may not be refused unless, of course, the challenged has a previous engagement.
In order to obtain victory in the Feats of Strength, one must pin their opponent to the ground. There are various definitions of what constitutes a "pin" during the duel, but the most common is the standard 3 count. (Some accept a "tap out" due to submission as an acceptable way to end the contest.) Until the head of the household is pinned, the Festivus celebration is not officially over.
* HowStuffWorks does not condone participation in the Feats of Strength without proper adult supervision and protective gear.