GMC 2010 Yukon/Yukon XL Owner's Manual page 16

If equipped, this control is located on the outboard side
of the seat.
To recline the seatback:
1. Lift the recline lever.
2. Move the seatback to the desired position, then
release the lever to lock the seatback in place.
3. Push and pull on the seatback to make sure it is
locked.
See Reclining Seatbacks on page 2 12.
1-10
If available, this control is located on the outboard side
of the seat.
To recline the seatback, tilt the top of the control
rearward.
To bring the seatback forward, tilt the top of the control
forward.
See Reclining Seatbacks on page 2 12.