Hand Valve Brake

• To make sure the 5th wheel is latched
• To hold the trailer in position as you slide tandems
• To check for application air leaks
• To activate auto slack adjusters with 80+ psi. You can do this with the foot valve but sometimes I prefer to isolate the action to the trailer only
• And a few other things

 

It’s a hand brake for the trailer.
There are some trailers that do not have spring brakes on them.
In the event that a non spring brake trailer has sat unused for a length of time the air brakes can leak off.
If you were to try to couple to it you could chase it all around the yard trying to get under it.
The old school way to couple to a trailer is back the fifth wheel so it just contacts the front of the trailer.
Then get out hook up air lines and light cord.
Get back in the truck charge the trailer with air and then apply the hand brake you are referring to and the back under the trailer.
So you see it would apply the trailer brakes when coupling so you don’t chase the trailer around yard trying to get under it.
There are also a few other uses for it but not recommended.

 

If you are an ice road trucker you use it to skid the tires around corners to make good TV

 

You're showing your age, old man

 

It's primary purpose is to pull your trailer back behind you when you're getting squirrely in the snow.

You GENTLY apply some brake to the trailer, and the tractor will pull it back behind you.

 

Headset holder

 

Two good uses

1. Set it down to get out and make sure your brake lights work.
2. Test your trailer service brakes

 

3. When pulling someone else's trailer, use it going downhill to conserve the tractor brakes. Use their brakes instead.