Lyda: "This is the first real embroidery stitch i learned, i used it on the seams of my apron dress." Vandyke stitch, several extant things have this on them in some form or another (see Medieval Clothing and Textiles vol VIII?
Ever wonder about all those feet that came with your sewing machine? This site has fun tutorials for everything and tips for the experienced and beginner alike. How to sew flat felled seams. This site has tutorials for other types of seams too.