Under the guise of "explaining the importance hand signals" during the match, NBC has about the most gratuitous photo gallery of women's backsides in teeny-weenie bikinis this side of Sports Illustrated's swimsuit issue. The whole idea of buttock aesthetics has received some attention in plastic surgery literature, and one of these days I'll write about it.
If you think I'm exaggerating about how blatant a T&A show the coverage is, please check NBC's gallery on the web which as far as I can tell was likely compliled by a 12 year old male NBC staffer!
Usually, in doubles competition, you have a server and you have his/her partner near the net. Crucial to a successful game play is a good line of communication between the players on a team as the court is a wide area for two players to cover. A lack of coordination between players will likely result in wide open spaces and a disjoint defense. It is up to the person nearest the net to call the shots and signal clandestinely to his/her partner what the intended game play is. In essence, the person nearest the net is the quarterback of the team.
There are 4 basic "modes" for each hand which is held behind the back to signal the other player. 'One finger' signals that the net player will block the opponent's spike down the line on the corresponding side of the hand. 'Two fingers' signals that the net player will block the opponent's spike at an angle cross-court on the corresponding side of the hand. A 'closed fist' signals that the net player will not block on the corresponding side of the hand. And finally an 'open hand' signals that the net player will block "ball," i.e. block according to how and where the opponent sets and swings.
I think this athlete's signaling she's wedging! :)