FORD 2011 F-550 v.4 - Manual (Page 205)

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.
Seating and Safety Restraints
205
2011 F-250/350/450/550 (f23)
Owners Guide, 4th Printing
USA (fus)