2003 GMC Sierra 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. 1-43