Other Tutorials:

Atefoub (beginning of video)

     The N-Box is a variation of the Box where the middle balls is passed between hands along a diagonal line, such that one hand is raising up to catch and slam the ball each cycle. The N-Box is one of the more difficult box variations, due to the speed and accuracy required from the throws and catches. Visually, the trick is quite appealing, especially when combined with other Box variations.

To learn the N-Box, it is important to practice the rather unique throw and catch combination that occurs on the raised side of the diagonal (i.e. the side where you lift your hand). The first throw is particularly unusual, since you are almost dropping the ball as you raise your over it hand to grab the diagonal pass. To practice this part of the trick, start with two balls, one in each hand. From you non-dominant hand, you are going to toss a ball upward diagonally toward your other side, while at the same time raising your dominant hand. As you lift that hand, you are going to drop its ball, which should continue to fly upwards for a short while due to inertia. You will then catch the first ball with your now empty dominant hand, and then quickly slam it back down to your other hand, claw catching the second ball as your dominant hand moves back down.
    Practice this over and over until you can execute it smoothly and consistently. If you do not have this two ball part of N-Box mastered, the next step will be much more difficult. To add in the third ball, it is best to start out juggling a normal Box pattern. Then, throw a ball up from your non-dominant hand diagonally toward the your other side, and then execute the unique throw and catch sequence in the previous step, slamming the ball back to your non-dominant hand. Then go back to the normal Box pattern.
    As you practice the N-Box, you should be able to decrease the number of normal Box "recovery" throws in between N-Box throws, eventually coming to the point where you can juggle them continuously.