GMC 1999 Sierra 1500 Pickup Owner's Manual page 264

Problems on the Road
"I
K2536
Attach the ratchet, with the DOWN marking facing you, to the wheel wrench.
Put the chisel end of the wheel wrench on an angle through the hole in the
rear bumper. Be sure the wheel wrench connects into the hoist shaft.
Turn the ratchet to the left to lower the spare tire. Keep turning the ratchet
until the spare tire can be pulled out from under the vehicle.
K2537
When the tire
has
been lowered,
tilt
the retainer at the end of the cable and
pull
it
through the wheel opening.