Oh we made one of these for our American Staffordshire/American pitbull mix, Kali.
Basically all we did was buy a garage door spring from Maslack (also can be found at Canadian Tire, Home Depot, and most hardware stores) and fastened it to a very sturdy tree branch using a heavy duty rubber strap used at my boyfriend's work (transport driver) that is the same as this, but much wider and thicker:
To attach this strap to the tree arm, we removed the hooks and used something that looks like this to connect both ends as well as the garage door spring - the only difference is that our fastener had a piece in the middle that screws to open/close:
This one is exactly what we used but ours is a bit thicker:
We used another of these fasteners at the bottom of the garage door spring to make changing the toy/rope/tire easier.
For a toy we used an old flat tow rope that we tied in knots. The bonus with this is that the thing is so long you can cut it into sections and keep some for backup when the one on the springpole gets destroyed. Looks like this, only we removed the hooks and ours is about 3 inches wide:
Another good thing to dangle from the spring is a wheelbarrow tire. They are pretty cheap and do not have any metal straps in them so they are safe for the dog to bite down on.
Also make sure you use a garage door spring because they are the most sturdy - trust me on this one! Trial and error proved that pitbulls can really stretch out crappy springs. They look like this:
WORD OF CAUTION:
People discriminate against pitbulls all the time. There are breed bans everywhere - including in my province (Ontario). Breed specific legislation is wrong, stupid, and insane which I'm sure all of you who have posted in this thread could agree. I've been advised by fellow pitbull owners that some animal control agencies and animal advocate groups have a list of items that dog fighters/rings commonly have on site and springpoles are on the list. If you have weird neighbors who hate your dog, dogs in general, or are just brainwashed by the media - please let them know why you have a springpole and that it is just a toy!
You can read more about this here:http://www.pitbulllovers.com/training-articles/pitbull-training-springpoles.html