Ford 1999 Explorer Owner's Manual page 139

The provision (attaching hole) is provided in the rear edge of the front
passenger seat cushion frame. The anchorbracket must be installed using
the instructions provided with the kit.
Tether anchorage hardware kits (part number 613D74) including
instructions, may be obtained at no charge from any Ford or
Lincoln-Mercury dealer.
Tighten the anchor according to specifications. Otherwise, the
safety seat may not be properly secured and the child may be
injured in a sudden stop or collision.
Seating and safety restraints
139