Buttonholed Double Chain is an unusual variety that I found this variation of double chain in The Constance Howard Book of Stitches (p 106).
This version of double chain is buttonholed and can feel messy but once past the first few stitches it takes on a form and behaves.
Work Buttonholed Double Chain stitch downwards between imaginary parallel lines.
Bring your needle up from the back of the fabric on the left hand side of the line and insert it on the right hand side with the needle pointing downwards. Position it a little to the right of where the thread emerged.
With the thread wrapped under the needle pull the needle through the fabric so that you create a very open chain stitch.
Instead of tying the chain stitch down, working from right to left, use the open chain stitch as a foundation to create 3 to 4 buttonhole stitches. At this stage of the stitch do not pass your needle through the fabric just buttonhole the bar.
When you have worked along the bar to the half way point make the second (openish) chain by inserting the needle into the fabric pointing downwards, on the left hand side of the line just below where the thread first emerged. (See the illustration)
To start the first buttonhole wrap the thread over the needle and under before pulling the needle through. This makes the second chain stitch which is a foundation bar for buttonhole stitches. Working left to right work 3-4 buttonholes stitches.
When you have worked along the bar once again at the half way point make the next open chain by inserting the needle into the fabric pointing downwards, on the right hand side of the line.
Once again to start the first buttonhole wrap the thread over the needle and under before pulling the needle through.
Continue in this manner back and forth down the line.
When you first start this stitch it feels sloppy and uncontrolled but once you get in the swing it forms an interesting line or worked row upon row develops into an interesting net like texture.