|Fusible thread can reduce the need for understitching. Put the fusible in the bobbin. Stitch on the garemnt side of the two fabrics when attaching the facings. After clipping the seamlines, turn the facings to the inside. Bring the right side of the fabric over slightly so the seamline is just out of sight of the right side. Press in place. This will bond the seam onto the front of the garment. On an unlined jacket you can serge the edge with fusible in the bobbin, turn the facing inside and press. This is from Australian Stitches, vol 7 no 2.