GMC Jimmy 2004 Owner's Manual page 34

Here's how to install a comfort guide and use the
safety belt:
1. Pull the elastic cord out from between the edge of
the seatback and the interior body to remove the
guide from its storage clip.
1-28
2. Slide the guide under and past the belt. The elastic
cord must be under the belt. Then, place the guide
over the belt, and insert the two edges of the
belt into the slots of the guide.