GMC Safari 2003 Owner's Manual page 61

If your child restraint does not have the LATCH system,
you'll be using the lap-shoulder belt to secure the
child restraint in this position. Be sure to follow the
instructions that came with the child restraint. Secure the
child in the child restraint when and as the instructions
say.
1. Put the restraint on the seat.
2. Pick up the latch plate and run the lap and shoulder
portions of the vehicle's safety belt through or
around the restraint. The child restraint instructions
will show you how.
3. Tilt the latch plate to adjust the belt if needed.
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