GMC 2001 Denali Owner's Manual page 64

Second Row Seat
4. Buckle, position and release the safety belt as
described in "Rear Seat Outside Passenger Positions"
earlier in this section. Make sure that the shoulder
belt crosses the shoulder.
Third Row Seat
To remove and store the comfort guides, squeeze the
belt edges together so that you can take them out from
the guides. Make sure you remove the comfort guide
from the belt before you fold a rear seat down.
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