This is the fourth play. The scholar wants to strike his head and then take his sword in the way that you see drawn here.
This play does not concern itself so much with the strike as what to do next. Beat your opponents sword to the right and strike along the inside line, similar to the 1st scholar of the 8th master. Having hit, but not necessarily killed or unhorsed your opponent, you are now disarming them.
Scoop your right hand back towards yourself so that you are contacting the inside of your opponents forearm with your own. Hook your hand so that the pommel goes over the top of their arm as shown. The movement of the horses will slide your forearm down to the wrist until your hand goes under the crossbars of the sword, levering it from their grip.
Although shown working from the inside of the arm, this play works equally well from the outside. If you make your initial strike from the left, as shown by the 2nd scholar of the 8th master, you can just as easily drop the pommel onto the inside of your opponents arm, sliding your forearm along the outside. Although the application is slightly different, the mechanics of the disarm are the same.
Having completed the play, you can safely turn to finish off your wounded and disarmed opponent. Although it does not appear earlier, there is absolutely no reason why you could not use this disarm with a sword in one hand when fighting on foot.