I'm guessing you are talking about the actual quilting part and not the piecing together. In the beginning this can be confusing to some. What matters is first if you want that look on both top and bottom, 2nd if you have any tension problems where the top thread shows up on the bottom and vice versa if it shows up on top, then using it in bobbin as well will make it blend so you don't see those issues. The other thing is that if you don't want to use it in bobbin (sometimes it cost more) then make sure bobbin thread is the same type as the needle thread, cotton, polyester, etc. I love using Aurifil and they also have pretty varigated threads that are low lint and hold up well to quilting. Good luck