56. You should not back a tractor under a trailer until the whole air system is:
At normal pressure
57. After you lock the kingpin into the fifth wheel, you should check the connection by:
Pulling the tractor ahead gently with the trailer brakes locked.
58. When should you use the hand valve to park a combination vehicle?
Never
59. You have coupled with a semitrailer. Where should you put the iron trailer supports before driving away?
Fully raised with the cranck handle secured in its bracket.
60. The safety catch for the fifth wheel locking lever must be ____ for a coupling to be complete.
Over the locking lever.