It should bend the LE's in slightly. With the slot in the knock aligned with the spreaders, the knot in the trick line sits toward the centre of the kite then the line runs to the outside and then back to the spine.
Lots of people used to take them off to try to do lazy susans but it spoils the feel of the kite if the LE isn't bent.
Don't bother with it!
Yeah its ancient but if he has one he might as well give it an airing.