GMC Sierra Denali 2009 Owner's Manual page 318

Dolly Towing (Rear Wheels Off the Ground)
Use the following procedure to dinghy tow a
two-wheel-drive vehicle from the rear:
1. Attach the dolly to the tow vehicle following the
dolly manufacturer's instructions.
2. Drive the rear wheels onto the dolly.
3. Firmly set the parking brake. See Parking Brake on
page 2-32.
4-42
4. Put the transmission in P (Park).
5. Secure the vehicle to the dolly following the
manufacturer's instructions.
6. Use an adequate clamping device designed for
towing to ensure that the front wheels are locked
into the straight position.
7. Turn the ignition to LOCK/OFF.