This trick was invented by ex TWJC member Danny Harrison several years ago. Danny & I used to compete with each other to come up with new tricks & patterns. This trick was one of his best efforts.
Take all three balls & juggle 441, sorry if you wanted to learn this trick from one tutorial but there is no easier way to learn this trick than to learn 441 first. As you juggle count out the throws to yourself. Start with the 'one' as the first vertical throw, the 'two' as the second vertical throw & the 'three' as the horizontal throw.
Now focus your attention on the horizontal 'three'. Notice that you catch the ball then toss it up as a vertical throw. This time catch the three, scoop it back the way it came & throw it Under the arm. Throw the ball so that it curves back to the same side. That is if you are throwing with the right hand, you scoop under the left arm, throw from the left of the pattern & catch the ball back on the right hand side of the pattern. Practise this one throw at a time. Making sure you maintain the 441 pattern all the time.
Keep practising adding in the occasional under the arm throw. Notice that the other arm instinctively dodges out of the way & circles around the ball thrown under the arm. Exaggerate the dodge into a full carry that orbits the under the arm throw. The carry is exactly the same as the one you would perform in the 423 Orbit pattern.
Begin the carry before you've even made the under the arm throw. As soon as you start to scoop your hand to make the under the arm throw carry the other ball up in an arc over where the ball will go. As the ball you're orbiting leaves your throwing hand carry the ball down. As the under the arm ball peaks continue the carry underneath & to the outside. Then throw the 'two' as normal & make the horizontal pass.
Work up to making an under the arm throw every time you catch a horizontal pass & make an orbit around every under arm throw too. You could stop there. That is in itself a very nice pattern. But Harrison's Hang is slightly different.
After making an orbit, you throw the carried ball straight up & pass another ball horizontally into the carrying hand once it is empty. In Harrison's Hang you carry the ball around a bit further, making sure that at the end of the circle you are holding the ball with your palm facing down. Flick your wrist back to throw the ball straight up. At the same time scoop the other hand to a point underneath the carrying hand & instead of making a horizontal pass throw the ball vertically up into the other hand. Flick your wrist back down & Claw the vertical throw. You'll find that the two vertical throws need to be made simultaneously. As soon as you make the claw catch carry the ball back down & make the under the arm throw on the other side. Repeat to continue.