Thanks. I tied rope through the holes in the bottom one and after making a knot, fluffed the ends. The second ball contains craft sticks and some bamboo chopstick pieces in the top and bottom row of holes. The top ball contains shredded paper stuffed into the holes.
I must warn you - it was not easy LOL!! After a while, it is very hard to thread the rope through and still find the end on the other side of the ball. Wrapping the end in sticky tape to make a solid tip, helps. I stuck the papers in wih a big crochet needle, as someone here (I think it was Betrisher) suggested.
I doubt that I will be making this again, too much work for too quick a destruction!

. Of course, if my boy loves it, then of course I will make him as many as he wants
Edited to add - I just saw you're from SA so I thought you'd like to know where I got the materials? The balls are golf practice balls from Game like in this picture.
The rope I bought at Builders Warehouse. They sell it by the meter.
The craft sticks I got at Mambo's - do you have one where you live?
The paper I cut up myself - yup, really. I take paper along on business trips to cut up at night in the hotel
