If you are making monogrammed towels, you hoop solvy on top and bottom of the towel so that your machine bits don't catch and pull the loops in the towel. You can use the same thread in the bobbin as the top, or you can use bobbinfil in the bobbin. When you have monogrammed the towel, you pull off most of the solvy then rinse away the left over bits as it dissolves in water.