Ford 2006 F150 Owner's Manual page 156

Seating and Safety Restraints
5. 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.
6. While pushing down with your
knee on the child seat pull up on
the shoulder belt portion to tighten
the lap belt portion of the
combination lap and shoulder belt.
7. Allow the safety belt to retract and remove any slack in the belt to
securely tighten the child safety seat in the vehicle.
8. Before placing the child into the
child seat, forcibly pull the child
seat forward and back to make sure
that the seat is held securely in
place. To check this, grab the seat
at the belt path and attempt to
move it side to side and forward and
back. There should be no more than
one inch of movement for proper
installation.
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