Why should the trailer hand brake not be used to straighten out a jackknifing trailer?

The correct rationale for avoiding the use of the trailer hand brake to straighten out a jackknifing trailer is that employing it can exacerbate the situation rather than remedy it. When the hand brake is engaged, it creates a significant amount of drag on the trailer's wheels. This dragging prevents the wheels from turning freely, which can result in a loss of traction. Consequently, if the trailer's wheels lock up, this can lead to a further loss of control and enhance the skid, making it difficult to regain stability.

In essence, utilizing the trailer hand brake can lead to increased sliding and reduced steering capability, worsening the jackknife scenario. This understanding highlights the importance of proper braking techniques and the need to maintain productive control of the vehicle rather than inadvertently contributing to a dangerous situation.