GMC 2002 Sierra - Manual (Page 63)

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Lower Anchorages and Top Tethers for
Children (LATCH System) (If Equipped)
Your vehicle may have the LATCH system. If it does,
you’ll find anchors (A) in the seat, where the seatback
meets the seat cushion. For front passenger seat
positions, there is an anchor behind and to the bottom of
the seat to secure the top strap. For rear center seat
positions, there is an anchor near the driver’s side rear
seat head restraint.
To assist you in locating the lower anchors for this child
restraint system, each seating position with the LATCH
system will have a visible metal anchor point in the seat
where the seatback meets the seat cushion.