GMC T-Series 2007, Owner'S Manual, Page: 156 / 356

Braking in Emergencies
With ABS, you can steer and brake at the same
time. In many emergencies, steering can help you
more than even the very best braking.
Trailer Brake Hand Control Valve
If your vehicle has this feature, the control
is mounted on the floor console.
This feature lets you
apply the trailer brakes
without applying the
tractor brakes.
You can apply the trailer brakes a little or apply
them all the way if you have to. Use this control only
when you are driving. Do not use it for parking or to
hold the rig on a hill.
{
CAUTION:
Using the trailer brake hand control for
parking or for holding the vehicle on a hill
may not keep the vehicle from rolling.
This can happen if someone hits the valve
by accident, or if air pressure bleeds from
the system. If the vehicle rolls, you or
others could be injured. To park the
vehicle or hold it on a hill, use the
parking brake properly.
156