Download CDL Prep app now

Scan QR code or get instant email to install app

Question:

You have connected the airlines to couple a tractor to the semitrailer. What should you do before backing under the trailer?

A Supply air to the trailer system, then pull out the air supply knob.

explanation

Step 9: Lock the Trailer Brakes
Pull out the "air supply" knob or move the tractor protection valve control from "normal" to "emergency." [California Commercial Driver Handbook]

Explore more questions

Take more free practice tests for other CDL topics with our cdl prep now!

Related Information

Comments

<img alt="" data-src="https://secure.gravatar.com/avatar/f79cda84d2c4b7b363385b30bb67cb0f?s=64&d=mm&r=g" class="lazyload" src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==" /><noscript><img src="https://secure.gravatar.com/avatar/f79cda84d2c4b7b363385b30bb67cb0f?s=64&d=mm&r=g" alt=""/>

Alkam 2126

4 years ago

It a great app to study for your CDL tests

<img alt="" data-src="https://secure.gravatar.com/avatar/f79cda84d2c4b7b363385b30bb67cb0f?s=64&d=mm&r=g" class="lazyload" src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==" /><noscript><img src="https://secure.gravatar.com/avatar/f79cda84d2c4b7b363385b30bb67cb0f?s=64&d=mm&r=g" alt=""/>

Cbow33

4 years ago

Great app

<img alt="" data-src="https://secure.gravatar.com/avatar/f79cda84d2c4b7b363385b30bb67cb0f?s=64&d=mm&r=g" class="lazyload" src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==" /><noscript><img src="https://secure.gravatar.com/avatar/f79cda84d2c4b7b363385b30bb67cb0f?s=64&d=mm&r=g" alt=""/>

Livvy2u

4 years ago

Mom

Leave a Reply Cancel reply