GMC 2010 Yukon XL Denali Owner's Manual page 49

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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