What is the primary purpose of using chocks?

The primary purpose of using chocks is to secure the trailer from rolling. When a vehicle or trailer is stationary, especially on an incline, chocks are placed under the wheels to prevent unwanted movement. This is crucial for safety, as it ensures that the trailer remains in a fixed position while loading or unloading, or when the vehicle is parked without additional support. Proper use of chocks alleviates the risk of accidents that can result from a trailer rolling away, which can lead to serious injuries or damage.

The other options, such as preventing air from escaping or assisting in coupling, do not directly pertain to the primary function of chocks. While chocks can indirectly protect the ground surface by providing stability, their primary role is firmly related to securing the vehicle or trailer during various operations.