What is an important action to take before coupling to cars?

Before coupling to cars, it's essential to verify that the cars and engines are properly secured. This action helps prevent any unintended movement that could lead to accidents or injuries during the coupling process. If the cars or engines are not securely parked, there is a risk that they could roll or shift, creating a hazard not just for the personnel involved but also for the equipment. Ensuring that the vehicles are properly secured gives operators the confidence to proceed with the coupling process safely.

Other options, while they may be important in different contexts related to rail operations, do not directly address the immediate and critical safety concern that proper securing of cars and engines does before coupling occurs.