FORD 2003 F-150 v.3 - Manual (Page 131)

If the safety seat is not anchored properly, the risk of a child
being injured in a collision greatly increases.
Tether strap attachment rear SuperCab only
There are three loops of webbing just above the back of the rear seat
(along the bottom edge of the rear window) in the SuperCab. These
loops are to be used as both routing loops and anchor loops for child
safety seat tether straps. For example, the center loop can be used as a
routing loop for a child safety seat in the center rear seat and as an
anchoring loop for child seats installed in the outboard rear seats.
Many tether straps cannot be tightened if the tether strap is hooked to
the loop directly behind the child seat. To provide a tight tether strap:
1. Route the tether strap through
the loop directly behind the child
seat.
2. Attach the strap hook onto the
loop behind an adjacent seating
position.
Seating and Safety Restraints
131