In andy800's example you can see it under the felt but I think I have seen them over the felt as well, but either wat it is very subtle and you won't notice it if you're not looking for it. I had played craps for over a decade before I read a book that mentioned it, and since then I have noticed it every time.
There is a very subtle North-South bump under the felt, directly in the center, under the words "CRAPS" and "DEALER and PLAYERS" and "Seven". It might be easiest to see at the lowest horizontal line, below the words "Any Craps."
https://imgur.com/a/nvRbLsA
In andy800's example you can see it under the felt but I think I have seen them over the felt as well, but either wat it is very subtle and you won't notice it if you're not looking for it. I had played craps for over a decade before I read a book that mentioned it, and since then I have noticed it every time.