Ford Windstar Owner's Manual page 177

Figure 2: Securing the detachable shoulder belt
Refer to "Seats" in this section for information on removing and
installing seats.
After re-installing the second row bench seat, make sure that the
safety belt is not twisted before you insert it into the detachable
anchor. A twisted safety belt may cause the retractor to work
improperly. Then insert the detachable anchor tongue into the
detachable anchor until you hear a "snap" and feel the latch
engage.
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