Hummer 2004 H2 Owner's Manual page 370

Center Roof Marker Lamps
1. Push in on the notch with a flat tool and pull the
lamp out.
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2. Turn the bulb socket counterclockwise and remove
it from the lamp housing.
3. Remove the bulb from the bulb socket.
4. Put the new bulb into the bulb socket.
5. Place the hook end of the lamp in place on one
side and push the other end of the lamp down
until it locks in place.