GMC 2008 Envoy Denali Owner's Manual page 16

To return the seat(s) to the original position, do the
following:
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.
1. Lift the seatback until it locks into the upright
position. Push and pull on the seatback to
make sure it is locked.
1-12
2. Return the head restraints to the upright position by
reaching behind the seat and pulling it forward until
it locks into place. Push and pull on the head
restraint to make sure that it is locked.
3. Flip the seat cushion back into place.