FORD 2009 F-550 v.1 - Manual (Page 213)

The passenger seats of your vehicle may be equipped with built-in tether
strap anchors located behind the seats as described below.
The tether anchors in your vehicle may be straps on the seatback or an
anchor bracket on the rear edge of the seat cushion or an anchor bracket
mounted to the body shell on the back panel.
The SuperCab rear seat has three straps behind the top of the seat back
that function as both routing loops for the tether straps and anchor
loops.
The tether strap anchors in your vehicle are in the following positions
(shown from top view):
• F-Series Regular Cab
• F-Series SuperCab
• F-Series Crew Cab
Attach the tether strap only to the appropriate tether anchor as shown.
The tether strap may not work properly if attached somewhere other
than the correct tether anchor.
Once the child safety seat has been installed using the safety belt, you
can attach the top tether strap.
2009 F-250/350/450/550 (f23)
Owners Guide, 1st Printing
USA (fus)
Seating and Safety Restraints
213