During any game day, while walking to the Coliseum, Trojan football fans (anyone who’s rooting for USC) kick the bases of the flagpoles at the end of Trousdale for good luck during the game.
On the way to the Coliseum (USC’s football stadium), it’s common to see fans passing into the stadium park to kick the flagpoles. The informant, as a marching band member, was told from the first game on to kick the pole as the band marched by, but other USC students find out from student friends or USC alumni at the games.
I spoke to my informant during an on-campus event.
It doesn’t appear that there is any real rational behind the practice? Maybe it’s like the theater practice of “breaking a leg” or the general saying “knock on wood,” with the caveat that since not all USC Trojan football fans are USC students or alumni, the flagpoles are a universally-recognized symbol that all fans can engage with.