2010 GMC Sierra 1500 Crew Cab Owner's Manual - Page 574

5. If the spare does not lower, turn the wrench counterclockwise until approximately 6 inches (15 cm) of cable is exposed. 6. Stand the wheel blocks on their shortest ends, with the backs facing each other. 7. Place the bottom edge of the jack (A) on the wheel blocks (B), separating them so that the jack is balanced securely. 8. Attach the jack handle, extension, and wheel wrench to the jack and place it (with the wheel blocks) under the vehicle toward the front of the rear bumper. 6-114