When cutting expensive sheer fabric it would be better to place tissue paper underneath. Some even place tissue paper under the seam all through. Stitch through both the tissue and the fabric. This way no fear of stretching and tearing the fabric at all. If you are not using a tissue, use a sheet of woven fabric on the cutting table where you will place the fabric, especially if you are cutting slippery sheer. Hold the fabric firmly with your free hand when cutting Some sheer fabrics like lace have a decorative edge along the length which you can use as a hem. Keep this in mind when calculating yardage for sewing as well as when laying out the fabric for cutting.