Download CDL Prep app now

Scan QR code or get instant email to install app

Question:

Before you back under a trailer, make sure that:

A The trailer brakes are locked.

explanation

Step 9: Lock Trailer Brakes - Pull out the \"air supply\" knob or move the tractor protection valve control from \"normal\" to \"emergency.\"

Explore more questions

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