Lexus 2003 LS Owner's Manual page 320

IN CASE OF AN EMERGENCY
40L080
2. Lift up the back side of the board and secure the board
by hooking the lever at the top of the trunk lid opening as
shown.
Make sure the board is secured and does not fall down.
306
40L081
When closing the board, replace the hook also in its
original position as shown.
NOTICE
If you close the trunk lid with the board hooked, the
hook may be damaged.