Lexus LS400 Owner's Manual page 118

16L161−2
2. Fully extend the shoulder belt to put it in the lock mode. When
the belt is then retracted even slightly, it cannot be extended.
To hold the infant seat securely, make sure the belt is in the lock mode
before letting the belt to retract.
COMFORT ADJUSTMENT
16L162−2
3. While pressing the infant seat firmly against the seat cushion and
seatback, let the shoulder belt retract as far as it will go to hold the
infant seat securely.
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