Hummer 2007 H3 Owner's Manual page 11

The seats have manual reclining seatbacks.
The lever used to operate them is located on
the outboard side of the seats.
To recline the seatback, do the following:
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.
To return the seatback to an upright position,
do the following:
1. Lift the lever fully without applying pressure
to the seatback and the seatback will return
to the upright position.
2. Push and pull on the seatback to make sure
it is locked.
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