Never | |
When unloading | |
When parking for less than 10 minutes | |
When parked on a grade |
When you start to recover from the jackknife | |
As soon as you start to jackknife | |
In the middle of the jackknife | |
Never |
Keeps water and dirt out of the lines | |
Saves wear on the dummy coupler | |
Maintains air tank pressure by keeping air from escaping | |
All of these are true |