GMC 2008 Yukon Denali Owner's Manual page 16

Folding and Tumbling the Seat(s) from the
Third Row Seats
CAUTION:
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Using the third row seating position while the
second row is folded, or folded and tumbled,
could cause injury in a sudden stop or crash.
Be sure to return the seat to the passenger
seating position. Push and pull on the seat to
make sure it is locked into place.
To fold and tumble the seat from the third rows, if your
vehicle has them, do the following:
1. Make sure that there is nothing under, in front of, or
on the seat.
Notice: Folding a rear seat with the safety belts
still fastened may cause damage to the seat or the
safety belts. Always unbuckle the safety belts
and return them to their normal stowed position
before folding a rear seat.
1-12
2. Lift the lever(s), located on the bottom rear of the
second row seat(s) on the inboard side, to release
the seatback. The seatback will fold forward.
3. Lift the same lever again to release the rear of the
seat from the floor. The seat will tumble forward
automatically.