Lexus 2003 LS Owner's Manual page 172

COMFORT ADJUSTMENT
16L311
1. Run the lap and shoulder belt through or around the infant
seat following the instructions provided by its manufacturer
and inserting the tab into the buckle taking care not to twist the
belt. Keep the lap portion of the belt tight.
CAUTION
A After inserting the tab, make sure the tab and buckle
are locked and that the lap and shoulder portions of
the belt are not twisted.
A Do not insert coins, clips, etc. in the buckle as this
may prevent you from properly latching the tab and
buckle.
A If the seat belt does not function normally,
immediately contact your Lexus dealer. Do not use
the child restraint system until the seat belt is fixed.
It cannot protect your child from injury.
158
16L312
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 retract.