Lexus RX400h2006 Owner's Manual page 270

5. Replace the head restraint and lift it up to the
uppermost lock position.
Be sure to close the cover when the anchor bracket is not in
use.
OCCUPANT RESTRAINT SYSTEMS
Installation with child restraint lower
anchorages
Lower anchorages for the child restraint systems
complying with the FMVSS225
specifications are installed in the rear seat.
The anchorages are installed in the seat cushion of the right
side seating position and between the center and left side
seating position.
or CMVSS210.2
243