Glad-hand shut-off valves at the rear of trailers (for connecting to a following trailer) must be:
Correct. Open the shut-off valves where the next trailer is connected; close them at the rear of the last trailer to prevent air loss.
CDL Practice Question #355
Category: Doubles/Triples
Why this question matters
This question is one of 50 in our Doubles/Triples bank. The reasoning above comes directly from the AAMVA CDL Manual, the source document used by every U.S. state DMV. Memorizing the underlying rule — not just the letter answer — is what separates passing on the first attempt from a return trip and another fee.