Chevrolet 2003 Silverado 1500 Pickup Owner's Manual page 50

Anchor the top strap to one of the following anchor
points. Be sure to use an anchor point located on the
same side of the vehicle as the seating position
where the child restraint will be placed. Raise the head
restraint and route the top strap under it.
Once you have the top strap anchored, you'll be ready
to secure the child restraint itself. Tighten the top
strap when and as the child restraint manufacturer's
instructions say.
Top Strap Anchor Location
Right Front Passenger Position Top
Strap Anchor (All Models)
You'll find the top strap anchor for the right front
passenger seat behind the seat, near the floor.
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