Chevrolet 2008 Equinox Owner's Manual page 32

There is one guide for each outside passenger position
in the rear seat. Here is how to install the comfort
guide to the shoulder belt:
1. Remove the guide from its storage clip on the
back 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.