Flat Stitch

According to Mary Thomas's Dictionary of Embroidery Stitches (1935): "The term 'flat stitch' is sometimes found in old embroidery books as referring to any embroidery worked in such stitches as satin, long and short, brick stitch and so on, all of which produce a 'flat' smooth effect."

Elegant Stitches, p 31 Mary Thomas's Dictionary of Embroidery Stitches, p 100 The Stitches of Creative Embroidery, p 70