In this trick the juggler bends forward at the waist and slides clubs down his back rather than throwing them.
Start with just one club and, leaning forward, place it on your back just over your shoulder blade so that you can see the end of the handle. Angle the club inward so that the body rests against your spine to stop it moving. Now straighten up slightly and allow the club to slide down your back, catching it with the opposite hand just above your bottom. Do this move until you can complete it confidently, and grab the club by the handle every time.
Now pick up the second club and hold it in the 'catching' hand, as opposed to the 'sliding' hand. Place the first club on your back and slide it down as before, at the same time throw the second club up, to be caught in the now empty catching hand. Lastly catch the club coming off your back. Repeat this move with two clubs until you are able to build up some speed and catch the clubs reliably.
To start the trick with 3 clubs, put one on your back and hold one in each hand. Start to slide the club that is on your back and then quickly put the club that is in your upper hand onto your back to replace it, but don't allow it to start sliding yet. At the same time make the throw from the lower to the upper hand and catch the club as it comes off your back.
The thing to remember here is that everything happens at once, and when everything has been caught, you can pause with a club resting by your shoulder. You are now in the same position that you started in, to keep the trick going just repeat the sequence over and over. Eventually you will learn the angle at which the clubs will slide slowly down your back, and you will not need to move your body up and down. When this happens the rhythm changes to a regular left, right one.
The backscratcher can also be done from both sides, with the hands alternating and placing clubs on the back as soon as there is a space. Note that now there is no throwing of clubs, the hands catch clubs coming down your back and carry them straight up to the other shoulder.