Ford Mercury Villager 1997 Owner's Manual page 168

Tethering to lap/shoulder belt tongue
To attach a tether strap to a lap/shoulder belt:
1. Route the tether strap under the headrest and between the
head restraint supports.
2. Hook the tether strap hook into the large hole at the end of the
tongue of the lap/shoulder belt directly behind the child seat
position.
3. Adjust the tether strap length until the hook is about one foot
behind the seatback.
4. Pull the shoulder belt until all of the belt is fully extended and
a click is heard. At this time the belt is in automatic locking
mode (child restraint mode.)
164