I use a disappearing ink marker to mark the lines then quilt on the lines. If you are hand quilting the lines might disappear before you finish your project so mark as you go. If you are machine quilting, the marks can last up to 48 hours but I have had them disappear within a few hours. It probably depends on the temperature and humidity. They wash out in the washer but don't iron over the marks before you wash them out or you might set the ink permenantly.