Lexus 2003 LS Owner's Manual page 146

COMFORT ADJUSTMENT
Seat belt comfort guides
16L291a
The seat belt comfort guides are installed on the outside
rear seats to relieve uncomfortableness from the
shoulder belt when it is applied closer to a child's neck (at
the age of 10 or so), by pulling the shoulder belt a little
forward.
Slide the seat belt comfort guide forward to adjust the
shoulder belt.
The seat belt comfort guide should not be in the forward
position for other purposes.
132
CAUTION
Always make sure the shoulder belt is positioned
across the center of the child's shoulder. The belt
should be kept away from the child's neck, and should
not fall off the child's shoulder. Failure to observe these
precautions could reduce the effectiveness of the seat
belt in an accident, causing death or serious injury.