During a rail class, what must a rider do when entering the arena?

When entering the arena during a rail class, it is crucial for the rider to immediately halt. This action is important for a couple of reasons. Firstly, halting allows the rider to establish control of their horse and maintain a safe environment in the arena, especially since other competitors may also be entering or circulating around the space at the same time. The halt gives the judges an opportunity to observe the horse's demeanor and readiness as well.

Moreover, it ensures that the horse is settled and prepared before moving into the specific designated patterns or movements required by the class. This initial pause helps to avoid any accidents or chaos that could arise from horses moving in different directions at once. Therefore, halting as soon as one enters the arena promotes safety and organization within the competitive setting.