Double herringbone stitch

First a row of herringbone stitch is done.

Then a contrast coloured thread is used to do double herringbone stitch. 

First the thread is fixed in between two stitches. 

Moving the needle below the second stitch to the lower line, a herringbone stitch is done as usual. 

To work the second stitch move the needle over the existing third stitch and do a regular herringbone stitch. 

For the next stitch again move under the existing thread and do the stitch. 

This process is continued to get a full row of stitches. 

The basic idea of herringbone stitch is that the second stitch overlaps the first one. 

Similarly in double herringbone stitch the first stitch is done by moving under the existing thread. 

The second stitch moves over the thread thus overlapping the first stitch. 

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I have used this stitch along the edge of the neckline.