Chevrolet 2010 Impala Owner's Manual page 58

Here is how to install a comfort guide to the safety belt:
1. Pull the guide out from the pocket on the edge
of the seatback.
2. Place the guide over the belt, and insert the two
edges of the belt into the slots of the guide.
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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.