Coaches often use signals in competition to tell players which play to run, which pitch to throw, where to attack or defend, and more. It’s the best way to remind a team what they need to do without letting the other team find out.
Not many know that a familiar Christmas carol was really a song of hidden messages. In the early 16th century, British Catholics were forbidden by law to practice their faith. Anyone caught speaking or writing of his or her faith was arrested or executed. In a time of persecution, similar to the Christians in Rome, Catholics in England went underground. They met and studied secretly and had signs to share their faith.