What should you ensure before backing under a trailer?

Before backing under a trailer, it is essential to ensure that the trailer brakes are locked. This is important because locked brakes prevent the trailer from rolling while you are maneuvering the towing vehicle into position. If the trailer were to roll, it could lead to an unsafe situation, potentially causing damage to both the trailer and the towing vehicle, or posing a risk to others in the area.

While other factors such as ensuring the vehicle is in park or making sure the trailer is empty might seem relevant, they do not directly address the primary safety concern of keeping the trailer stable during the backing process. Operational windshield wipers are also not relevant in this context, as visibility issues while backing up are typically not a concern as long as proper precautions are taken. Ensuring that trailer brakes are locked is a fundamental step for safe and effective coupling in towing operations.