Hummer 2004 H2 Owner's Manual page 92

To use one of the locks, do the following:
1. Open one of the rear doors.
3. Close the door.
4. Do the same thing to the other rear door.
2-12
2. Turn the lock
counterclockwise with
your ignition key to
engage the rear door
security lock.
The rear doors or your vehicle cannot be opened from
the inside when this feature is in use. If you want to
open the rear door while the security lock is engaged,
unlock the door and open the door from the outside.
To disengage the child security lock feature, turn
the lock clockwise with your ignition key.
Lockout Protection
This feature protects you from locking your key in the
vehicle when the key is in the ignition and a door
is open.
If the power lock switch is pressed when a door is open
and the key is in the ignition, all of the doors will lock
and then the driver's door will unlock.