Lexus RX330 2005 Owner's Manual page 239

OCCUPANT RESTRAINT SYSTEMS
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1 Anchor brackets
Use the anchor brackets on the back of the rear seatback to
attach the top strap.
Anchor brackets are installed for each rear seating position.
This symbol mark indicates the location of the anchor brackets.
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2 Symbol mark 1. Remove the head restraint.
2. Open the cover of the anchor bracket.