GMC 2006 Sierra - Manual (Page 512)

4. Make sure the jack head is positioned so that the
rear axle is resting securely between the grooves
that are on the jack head.
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.
Front Position - All Other Models Rear Position
5-100