GMC 2009 Sierra 1500 Crew Cab Owner's Manual page 513

CAUTION:
{
Getting under a vehicle when it is jacked up is
dangerous. If the vehicle slips off the jack, you
could be badly injured or killed. Never get under
a vehicle when it is supported only by a jack.
CAUTION:
{
Raising your vehicle with the jack improperly
positioned can damage the vehicle and even
make the vehicle fall. To help avoid personal injury
and vehicle damage, be sure to fit the jack lift
head into the proper location before raising the
vehicle.
5. Turn the wheel wrench clockwise to raise the
vehicle. Raise the vehicle far enough off the ground
so there is enough room for the spare tire to fit
under the wheel well.
6. Remove all the wheel
nuts and take off the
flat tire.
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