Pontiac 2003 Montana Owner's Manual page 75

For vehicles with a full bench seat in the third row, there
is no top strap anchor in the driver's side position. Do
not secure a child seat in this position if a national
or local law requires that the top strap be anchored, or if
the instructions that come with the child restraint say
that the top strap must be anchored.
If your child restraint does not have the LATCH system,
you'll be using the lap-shoulder belt to secure the
child restraint. 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.
Third Row Outside Passenger Position
In the third row, tilt the latch plate to adjust the belt
if needed.
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