FORD 2010 F-150 v.3 - Manual (Page 206)

If you are using a Regular Cab center seat, see Installing child safety
seats in cinch tongue combination lap and shoulder belt seating
position later in this chapter for instructions.
Perform the following steps when installing the child seat with
combination lap/shoulder belts:
Note: Although the child seat illustrated is a forward facing child seat,
the steps are the same for installing a rear facing child seat.
1. Position the child safety seat in a
seat with a combination lap and
shoulder belt.
2. Pull down on the shoulder belt
and then grasp the shoulder belt
and lap belt together.
Seating and Safety Restraints
206
2010 F-150 (f12)
Owners Guide, 3rd Printing
USA (fus)