Hand signals in sports

America's favorite pastime, namely Baseball (glorified Rounders for you Brits), makes extensive use of hand signals. It is a very elaborate affair. Not just signals to give direction to teammates, but signals by referees and so forth.

I was looking for a video I had seen in the past that was set to music and showed loads of crazy signals strung together by multiple base coaches.

But, I found a three part documentary on the entire subject of hand signals in baseball. An interesting point I heard at the outset was how they initially worked with deaf mute folks due to their use of American Sign Language, which is on interest on its own.

Here is a short teaser/trailer to give you an idea of what goes on in baseball.

Signs of the Time Teaser Trailer

And here is the link to a longer video about the making of the documentary.

Making "Signs of the Time"

In horse racing / greyhound racing betting, the bookmakers have a complex system of hand signals, known as tic tac
It's explained in this video