Cadillac 2008 DTS Owner's Manual page 31

There is one guide for each outside passenger position
in the rear seat. Here is how to install a comfort
guide to the safety belt:
1. Remove the guide from its storage pocket on the
side of the seatback.
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.
3. Be sure that the belt is not twisted and it lies flat.
The elastic cord must be under the belt and the
guide on top.
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