Pontiac 2003 Montana Owner's Manual page 156

Notice: Loading cargo that weighs more than 150
lbs. (68 kg) on the luggage carrier may damage your
vehicle.
When you carry cargo on the luggage carrier of a
proper size and weight, put it on the slats, as far forward
as you can. Then slide the crossrail up against the
rear of the load, to help keep it from moving. You can
then tie it down.
2-52
Don't exceed the maximum vehicle capacity when
loading your vehicle. For more information on vehicle
capacity and loading, see Loading Your Vehicle on
page 4-32 .
To prevent damage or loss of cargo as you're driving,
check now and then to make sure the luggage
carrier and cargo are still securely fastened.
Turn the release knob counterclockwise to unlock the
crossrails. Slide the crossrails forward or back, as
needed, to accommodate loads of various sizes.
After repositioning the crossrails, be sure to tighten the
release knobs by turning them clockwise. This will
lock the crossrails in place.
Your luggage carrier has
release knobs set in the
ends of each crossrail.