Angela Walters explains it well.....you set the ruler on the quilt with the edge where you want the stitches to go. then you use the ruler as a "sort of a handle" to move the quilt keeping the edge of the ruler up against the side of the foot. This is why we need that special ruler foot as it has a higher edge to keep the ruler from getting under the needle which would not be good! It helps if the ruler has some sort of a grippy surface so it does not slide around on the fabric....some use those plastic dots that adhere to the bottom of the ruler but there is also special tape you can apply. The Angela Walters rulers has a rough surface on the bottom that helps the ruler stay in place on the fabric. I also use quilting gloves to help me move the quilt.