Chevrolet 2003 Avalanche Owner's Manual page 50

This system, designed to make installation of child
restraints easier, does not use the vehicle's safety belts.
Instead, it uses vehicle anchors (A, B) and child
restraint attachements to secure the restraints. Some
restraints also use another vehicle anchor to secure
a top tether strap (C).
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In order to use the LATCH system in your vehicle, you
need a child restraint designed for that system.
To assist you in locating the lower anchors for this child
restraint system, each seating position with the
LATCH system has a visible metal anchorage point in
the seat where the seatback meets the seat cushion.