Ford Villager Owner's Manual page 137

Features
Childproof Lock for the Sliding Door
Your vehicle has a childproof lock for the sliding door. If you
set the childproof lock, the sliding door cannot be opened from
inside the vehicle.
This lock will keep children from opening the door from the
inside; the door can still be opened from the outside if the door
is unlocked.
Childproof lock location
139