GMC 2007 Sierra - Manual (Page 62)

For regular cab models with a bench seat, the top
tether anchors are located under trim covers on the
back panel behind the center and passenger seats.
Do not install a child restraint in the center seat
position. See Securing a Child Restraint in the
Center Front Seat Position on page 74 for more
information. For regular cab models with bucket
seats, the top tether anchor is located under a trim
covers on the back panel behind the passenger
seat. Remove the trim plug to access the anchor.
For extended cab models, the top tether anchors
are located near the top of the seatback for
each rear seating position. In addition to the
top tether anchors, each seating position has a
fabric loop at the top of the seatback that you will
use to route the top tether through. Be sure to
use an anchor located on the same side of
the vehicle as the seating position where the child
restraint will be placed.
Regular Cab
Extended Cab
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