Hummer 2005 H2 - Manual (Page 137)

Tonneau Cover (SUT)
{ CAUTION:
If you remove the tonneau cover, do not store it
in the vehicle without securing it to the vehicle.
An improperly stored tonneau cover could be
thrown about the vehicle during a collision or
sudden maneuver. You or others could be
injured. When you put the cover back on,
always be sure that it is securely reattached.
Your vehicle may have a hard tonneau cover, you can
use it to cover items in the cargo area of your vehicle.
Your tonneau cover will have two lock cylinders on it.
One lock cylinder is to secure the cover closed and
the other lock cylinder will allow you to secure the
tailgate close.
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