GMC 2008 Yukon Denali Owner's Manual page 21

To return the seatback to an upright position, do the
following:
1. Lift the lever fully without applying pressure to the
seatback and the seatback will return to the upright
position.
CAUTION:
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If the seatback is not locked, it could move
forward in a sudden stop or crash. That could
cause injury to the person sitting there. Always
push and pull on the seatback to be sure it is
locked.
2. Push and pull on the seatback to make sure it is
locked.
Manual Fold and Tumble Feature
Folding and Tumbling the Seat(s)
To fold and tumble the seat, 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.
2. Lift the lever, located on the outboard side of the
seat, to release the seatback.
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