In order to work the motif, a double line of tiny dots is drawn down its middle, rather than a single line as with the fishbone stitch. Then to work the stitch, the thread is brought up at (1) and taken to (2). It then enters the cloth and comes out again at (3). The thread is taken to (4) where it re-enters the cloth. The thread is brought out again at (5) and the whole process is started once more.
Source: THOMAS, Mary (1934). Mary Thomas’s Dictionary of Embroidery Stitches, London: Hodder and Stoughton, pp. 98-99.
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