Chevrolet 2000 Express Van Owner's Manual page 51

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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