GMC 2007 Yukon XL Owner's Manual page 34

Unfolding the Seatback(s)
To return the seatback to the upright position, do
the following:
1. Open the liftgate to access the controls for
the seat.
2. Pull up on the seatback until it locks into the
upright position.
CAUTION:
{
If the seatback is not locked, it could
move forward in a sudden stop or crash.
That could cause injury to the person
sitting there. Always push and pull on the
seatback to be sure it is locked.
3. Push and pull on the seatback to make sure it
is locked.
34
Tumbling the Third Row Seat
The seat can be tumbled forward for additional
cargo space.
To tumble the seat, do the following:
1. Open the liftgate to access the controls for
the seat.
2. Make sure the head rests are completely
lowered, there is nothing under, in front of,
or on the seat, and all items are removed from
the cupholder and storage bin, if the seat is
a two-passenger seat.
3. Fold the seatbacks forward using the
instructions listed under "Folding the
Seatbacks" previously. You will not be able
to unlatch the seat from the floor unless
the seatback is folded down.