In doubles table tennis, the two players are required to hit the ball in an alternating fashion. This means that one player is free to play a shot on a second table while his partner plays a shot on the first.

So, a small number of ping pong tables are positioned along the edge of a regular polygon, say four tables to a square for example, and each pair of players stands at a vertex . There is one ball for each table. Services are synchronized, and proceed in the clockwise direction. One player from a team serves, while the other receives. After each player hits the ball, he must turn around and play the ball from the other table next to him, and so on. A pair can score one point per round for each winner it hits. The set ends when a team scores the required number of points.
-- Cuit_au_Four, Jul 29 2012

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