Double Chain Stitch is also called as Turkmen Stitch and is done by working the stitches across two parallel lines. It is a variation of chain stitch where each chain is pulled into alternating triangles.
Bring the needle up at 'a' go back down at 'b' and come up at 'c', placing the needle's point over the thread and pull through.
Next, go back down at 'a' and come up at 'd', placing needle's point over thread and pulling thread through.
Go back down at 'c' and come up at 'e', continue alternating the stitches from top to bottom edges till the end of the row.
Double Chain Stitch Back