For the love of all that is good and holy, please do not attempt to navigate the main rulebook. It's a maze of confusion.
Section 1: The Foosball Canon. In short, we're not really sure, but it's something like 5 inches.
Please, for the love of all that is sane, refer to our Handbook of Sanity for further guidance.
And that's it, folks! Now, if you'll excuse us, we have some scheduling to attend to.