Ford 1998 Windstar Owner's Manual page 110

The outside sliding door handle
Memory Lock
If you lock your doors with the power lock switch or the
remote transmitter while the sliding door is open, the door will
automatically lock after it is closed.
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.
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