GMC Sierra Denali Owner's Manual page 52

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With this system, use the LATCH system instead of the
vehicle's safety belts to secure a child restraint.
If a LATCH-type child restraint isn't attached
its anchorage points, the restraint won't be
able to protect a child sitting there. In a crash,
the child could be seriously injured or killed.
Make sure that a LATCH-type child restraint is
properly installed using the anchorage points,
or use the vehicle's safety belts to secure the
restraint. See "Securing a Child Restraint
Designed for the LATCH System", "Securing a
Child Restraint in the Right Front Seat
Position" or "Securing a Child Restraint in a
Center Rear Seat Position" in the Index for
information on how to secure a child restraint
in your vehicle.
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