FORD 2012 F-550 v.3 - Manual (Page 208)

3. While holding both shoulder and
lap portions next to the tongue,
route the tongue and webbing
through the child seat according to
the child seat manufacturer’s
instructions. Be sure that the belt
webbing is not twisted.
4. Insert the belt tongue into the
proper buckle for that seating
positions until you hear a snap and
feel it latch. Make sure the tongue is
securely latched to the buckle by
pulling on the tongue.
5. Remove remaining slack from the
belt. Force the seat down with extra
weight, e.g., by pressing down or
kneeling on the child restraint while
pulling up on the shoulder belt in
order to force slack from the belt.
This is necessary to remove the
remaining slack that will exist once
the additional weight of the child is
added to the child restraint. It also
helps to achieve the proper
snugness of the child seat to the vehicle. Sometimes, a slight lean
towards the buckle will additionally help to remove remaining slack from
the belt.
Seating and Safety Restraints
208
2012 F-250/350/450/550 (f23)
Owners Guide, 3rd Printing
USA (fus)