Double chain stitch
This is a variation of chain stitch where each chain is pulled into alternating triangles, forming a wide line.
This stitch is very similar to closed feather stitch: for this stitch the loop of the chain is taken down inside the loop of the previous chain; for closed feather the needle is taken down just outside the previous loop.
For more information, see the entry for chain stitch.
Double chain stitch was certainly being used in 16th century Europe as it features on a Swiss or south German ecclesiastical embroidery currently held in the Cleveland Museum of Art. Its use was not restricted to Europe as it also features on a mid 19th century Suzani (embroidered panel) from Turkestan and a cape from late 19th century Kashmir.
Imagine (or draw) two parallel lines which you want your stitching to fill.
Bring your needle out almost at the top of your left line, and down slightly higher on your right line.
Leaving a loop, bring the needle up on your right line, but a little lower than where you first brought the needle up.
Make sure you bring you needle up within the loop, and tighten to create a triangular stitch.
Take the needle back down on the left line (in the same hole in which you first brought the needle up) again leaving a loop.
Bring the needle out on the left line below where the previous stitch started, making sure you bring your needle up within the loop. Pull taught to create a second triangle.
Take the needle back down on the right line in the same place as the previous stitch started, leaving a loop.
Bring the needle out on the right line below where the previous stitch started, making sure you bring your needle up within the loop. Pull taught to create another triangle.
Continue working from side to side. When finishing the stitch take the needle down over the last loop to form a small anchoring stitch.
Structure of stitch
Mrs Archibald Christie, Samplers and Stitches (1921) , p.44–5
Mary Thomas, Mary Thomas’s Dictionary of Embroidery Stitches (1934) , p.36–7
Anne E. Wardwell. (1980) 'The Holy Kinship: A Sixteen-Century Immaculist Embroidery', The Bulletin of the Cleveland Museum of Art pp.285-295. Available at: https://www.jstor.org/stable/25159697
'Embroidered Panel: Holy Kinship', Cleveland Museum of Art. Available at: https://www.clevelandart.org/art/1979.1 (Accessed: 06 October 2021)
Mairead Reynolds. (1985) 'Suzani Embroideries', Irish Arts Review (1984-1987) pp.62 (1 page). Available at: https://www.jstor.org/stable/20491769
'Kashmiri cape', Victoria and Albert Museum (2009). Available at: https://collections.vam.ac.uk/item/O477099/cape-unknown/ (Accessed: 06 October 2021)