Chevrolet 2007 Monte Carlo Owner's Manual page 37

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. Pull the elastic cord out from between the
edge of the seatback and the interior body
to remove the guide from its storage clip.
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.
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