| 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 |
| Lock the trailer brakes and pull backward slowly then inspect the connection | |
| Release the trailer brakes and pull forward slowly then inspect the connection | |
| Pull forward quickly to stress the connection | |
| Lock the trailer brakes and pull forward slowly then inspect the connection |
| Pull out the trailer air supply valve | |
| Push in the trailer air supply valve | |
| Activate the air generator | |
| Activate the service line |