Question If a truck is equipped, a trailer brake hand valve can be used to: Answers Add fuel to the vehicle. Prevent the vehicle from rolling back when being started from a stop. Check the oil level. Load cargo. Explanation If a tractor-trailer is so equipped, the trailer brake hand valve can be used to stop the vehicle from rolling back when being started from a stop. Take a FREE Practice Test Now This questions appears in the following tests: Florida Knowledge Test Class A , Delaware Knowledge Test Class B , Nevada Knowledge Test Class B , North Carolina Knowledge Test Class B , Montana Double ,