Hummer 2003 H2 Owner's Manual page 16

Third Row Single Seat (If Equipped)
Folding the Seatback
CAUTION:
If the seatback isn't locked, it could move forward
in a sudden stop or crash. That could cause injury
to the person sitting there. Always press rearward
on the seatback to be sure it is locked.
1-10
To fold the seatback, do the following:
Unfolding the Seatback
1. To return the seat to the passenger position, pull up
on the release lever labeled 1 and then pull up on the
seatback until it locks into the upright position.
2. Push forward on the seatback to make sure it is
locked into position.
Pull up on the release lever,
labeled 1, located on the
rear of the seatback and
push the seatback forward.