In the movie, the people of District 12 hold up a three finger salute as Katniss and Peeta are taken to the capitol to compete in the 74th annual Hunger Games. They do this again in Catching Fire, in District 11 on the Victory Tour, as Katniss is giving a speech about Rue and Thresh. Before the rebellion started, the three finger salute meant saying goodbye to a loved one, wishing one good luck, etc. After the rebellion had started, this three finger salute was found as a horrible crime, as Katniss was the Mockingjay. When someone did hold up the three finger salute, they were sentenced to death on the spot. In Mockingjay, it is the symbol of the rebellion.