FORD 2003 Explorer Sport Trac v.1 - Manual (Page 105)

If you install a child seat with rigid LATCH attachments, do not tighten
the tether strap enough to lift the child seat off the vehicle seat cushion
when the child is seated in it. Keep the tether strap just snug without
lifting the front of the child seat. Keeping the child seat just touching the
vehicle seat gives the best protection in a severe crash.
Each time you use the safety seat, check that the seat is properly
attached to the lower anchors and tether anchor. Try to tilt the child
seat from side to side. Also try to tug the seat forward. Check to see if
the anchors hold the seat in place.
If the safety seat is not anchored properly, the risk of a child
being injured in a crash greatly increases.
Seating and Safety Restraints
105