I would like to make a checkerboard pattern around a 8" cake, similar to this: http://kellyssweetcreations.files.wordpress.com/2010/09/august-2010-101.jpg

Do I have to use a specific size square cutter?

I probably make this harder than it needs to be, but here's what I do.  I measure the circumference of the cake and figure out how many squares I need based on how big I want the squares.  Then I roll out fondant to a uniform thickness and use a food dedicated ruler to mark the size of the squares. Then I use a pizza cutter to make strips.  Measure and cut again to make squares.  I straighten and square up any edges that need it and let the squares firm up a bit before applying to the cake.  Make sure you start at the front so that if they don't connect perfectly it will be hidden in the back.

yes.  Measure the actual circumference of the fondanted cake, then find a number that is evenly divisible by 2 

"Fun with math."

You could also buy some square cutters like the ones below (use the smallest or 2nd to smallest). Just start in the front that way if they do not meet up perfectly, it will be in the back of the cake. I find that they usually aren't off by much & it's the back of the cake so it doesn't really matter.

http://www.amazon.com/dp/B0017Z5EYO/?tag=cakecentral-20+cutters
 

http://www.amazon.com/dp/B0000DE126/?tag=cakecentral-20+cutters

http://www.amazon.com/dp/B004BPQTKK/?tag=cakecentral-20+cutters

ADid the checkerboard on an 8" and should have stopped at the sides. Didn't have the fore thought then continued ove the top edge....still turned out okay though. [IMG]http://cakecentral.com/content/type/61/id/3259743/width/200/height/400[/IMG]