GMC 2010 Yukon XL Denali Owner's Manual page 95

Second Row Seat
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.
60/40 Third Row Seat
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.
Do not secure a child restraint in a position without a
top tether anchor if a national or local law requires that
the top tether be attached, or if the instructions that
come with the child restraint say that the top tether
must be attached.
Three Passenger
2-63