This lesson uses the vertical multiplex throw to the other hand which can be marked as [4x3] or [33]. Since no-one can catch two balls at the same time, the first notation is more realistic, and I use that in the simulator. It also emphasizes that one has to reserve more time to catch two balls so the throws must be higher. On the other hand, the latter notation makes the overall pattern much easier for a human to read and remember. For instance the goal pattern of this lesson can be written either as 4x1xL[4x3]0* or simply 3[33]0.
Step 1 Hold one ball with your thumb, index, and middle fingers, and the other ball in your palm. When throwing, keep your wrist relatively loose but fingers relatively stiff. This will help making the throw consistent. Try to get the balls well separated by using your wrist, not the fingers. Catch the first ball in your fingers and second one in your palm.
Step 2 Two throws.
Step 3 You are done. Try to throw the single ball before or at the same time as the others land to keep the action going on.
Mixing This pattern mixes easily with the horizontal multiplex.
Four-ball multiplex pattern in Lesson 34 is a direct extension of this pattern. If you had no difficulty here, you might want to skip ahead and try that immediately.