What is the most important hand signal that you and the helper should agree on?

The most important hand signal that should be agreed upon between you and your helper is to stop. This signal is crucial for ensuring safety, as it allows both parties to quickly halt any ongoing activity or movement, especially in potentially dangerous situations. When working in environments that require communication, such as guiding a vehicle while reversing or maneuvering in tight spaces, having a clear and understood signal for stopping can prevent accidents and injuries.

While signals for going forward, turning left, or speeding up are also important, they can be executed with more flexibility compared to the necessity of halting action immediately. The stop signal provides a clear, universal method of communication that significantly contributes to maintaining safety and preventing mishaps in various situations.