Pontiac 2004 Montana Owner's Manual page 75

The anchor bar for the stowable bench seat is located
on the passenger's side of the crossbar. Use the center
seating position to use the anchor bar properly. If the
convenience center is in the vehicle, you must lift
the tray sill to use the anchor.
Do not use a child restraint with a top strap in the right
front passenger's position, because there is no place
to anchor the top strap.
Third Row (Stowable Seat)
1-69