Fray Check can leave a stain on the fabric, so if you use it on the seams and it creeps over into the quilt block, it will leave a mark on it. I have a hard time using Frey Block by June Taylor. It has a huge hole that the liquid comes out o,f and it ends up everywhere. Maybe others have some hints on using it, but I've given up on it. Now if I have a fabric that ravels a lot, I use a very short stitch. If it has raveled so much that the seam allowance ends up being a eighth of an inch, I run a second line of stitching on the seam allowance close to the first line that has been stitched. I've had to do this once in a while and have had good success with it.