GMC 2008 Yukon Denali Owner's Manual page 68

Second Row Seat — 60/40
For models with 60/40 second row seating, the top
tether anchors are located at the bottom rear of the seat
cushion for each seating position in the second row.
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.
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Third Row Seat — Two or Three Passenger
For vehicles with a two passenger third row seat, there
is one top tether anchor located at the bottom rear
of the seat cushion that can be used for the rear driver
side seating position in the third row. Never install
two top tethers using the same top tether anchor.
For vehicles with a three passenger third row seat, there
is one top tether anchor located at the bottom rear of
the seat cushion that can be used for either the third row
center or driver side seating position. Never install
two top tethers using the same top tether anchor.