There are two main hand gestures that bikers use (with index and middle fingers) while riding. The first is the "double file" gesture, where a rider raises two fingers up.

Extend Two Fingers Settle on which fingers you'll be using for the whistle. “It’s a personal choice,” says Rainstrom, who tends to go with her two pointer fingers.

From Drake to Eminem, Jay Z, Lil Wayne and Kanye West, rappers have a thing for pointing. Check out some pics of them showing off their index finger in the most random of situations.