Ford Windstar Owner's Manual page 198

Pull the shoulder belts out to ensure that the crotch safety
8.
belt buckle and chest clip are securely fastened. Refer to
Figure 7.
Figure 7: Checking for securely latched buckle and chest clip
Pull left shoulder belt fully out to put the retractor into the
9.
lock mode. Allow belts to retract and fit snugly. The purpose
of the lock mode is to prevent the child from getting out of
the seat while the vehicle is in operation and to hold a
sleeping child in position. The belts will lock automatically
during a collision or hard braking.
Seating and Safety Restraints
197