GMC Sierra 1999 Owner's Manual page 283

Turn the wheel wrench clockwise to raise the jack lift
head a little.
Remove the hub cap.
If the wheel has a smooth center piece, place the chisel
end of the wheel wrench in the slot on the wheel and
gently pry out.
yellowblue
If your vehicle has wheel
nut caps, loosen them by
turning the wheel wrench
counterclockwise. If you
have a center cap with
wheel nut caps, the wheel
nut caps are designed to
remain with the center cap.
5-23