I've seen cakes that have diagonal rows of imprints that end up looking like diamond shapes and sometimes pearls are added where the lines intersect. How do you make those lines? They are really beautiful!

You can use a diamond impression mat on the side of the cake to get that design: http://www.cakesbysam.com/store/cart.php?target=product&product_id=21524&substring=diamond+impression+mat

definitely recommend the mat, I tried it with a ruler and a knife and it's really hard to keep all the lines the same distance apart while maintaining the same angle.

I think I may have to get one of those mats. Not that bad of a price.

I have made two cakes with this diamond impression.
First one (baptism cake) I just used a knife.
2nd cake (bridal shower) I used a square cookie cutter and imprinted the cake ( i obivoulsy turned the cookie cutter to make it a diamond!!)
Both ways weren't perfect....but it did the trick

For those who have used the mats, this might be a silly question but, when you use them on fondant, do you make the impression first or after you put the fondant on the cake? I've seen pictures of cakes that have that design just on the sides, I'm assuming it's done after but I want to be sure. Thanks!

Thank you everyone! I ordered a mat today! I can't wait to make a cake with it.