GMC 2007 Yukon XL Owner's Manual page 59

CAUTION:
{
A safety belt that is not properly worn may
not provide the protection needed in a
crash. The person wearing the belt could
be seriously injured. The shoulder belt
should go over the shoulder and across
the chest. These parts of the body are best
able to take belt restraining forces.
4. Buckle, position, and release the safety belt
as described in Rear Seat Passengers on
page 54. Make sure that the shoulder
belt crosses the shoulder.
To remove and store the comfort guides, squeeze
the belt edges together so that you can take
them out of the guides. Slide the guide into its
storage pocket.
59