GMC Yukon Denali 2003 Owner's Manual page 51

There is one guide available for each outside passeger
position in the rear seats. Here's how to install a
comfort guide and use the safety belt:
Second Row Seat
1. For the second row, remove the guide from its
storage clip on the trim panel near the side of
the seatback.
Third Row Seat
For the third row, remove the guide from its storage
clip on the side of the seatback.
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