It looks like it was done with an impression mat. earlenescakes.com sells one.
you can use the impression mat as karateks said or the 3 diamond quilter. I have both and prefer the 3 diamond quilter, more control, especially around corners
I've used the diamond impression mat on fondant, but you have to do it while the fondant is fresh on the cake or it'll be too stiff to take the impression without cracking. I also went back over the lines with an embossing wheel just to make sure the lines were very defined. But, I think a quilter would work better. Pix I've seen of cakes done with a quilter just look better; the impression goes deeper and the lines are sharper and more defined. I think you can get them in different sizes, too.
Thanks lot guys! I can always count on u for helpl!!