Ford 1999 Wagon-Econoline Owner's Manual page 75

Always latch the vehicle seat to the floor, whether the seat is
occupied or empty. If not latched, the seat may cause injury
during a sudden stop.
Quick release captains chair
To remove the seats:
1. Disengage the lap/shoulder belt
from the seat by inserting a key or
small screwdriver into the slot in the
detachable anchor and lifting
upward.
Stow the tongue end of the
detachable anchor.
Seating and safety restraints
75