Buttonhole edging

This version of buttonhole stitch, as its name suggests, is used to edge fabric. The stitch is completed before the fabric is trimmed and thus lends itself to creating decorative hems.
For an introduction to the basic stitch, see buttonhole stitch.
For an alternative method of working this stitch where the fabric is trimmed before the stitch is worked, see buttonhole edging (variation).
Method
Work a line of double running stitch just outside the outline. To begin buttonhole stitch, bring the needle up just inside the line and take it down just outside the line, leaving a loop.
Bring the needle up just inside the line, right next to the first stitch, with the needle inside the loop.
Pull the excess thread to the back and then bring the needle and thread through and pull taut to complete the stitch.
Working clockwise, repeat around the shape, placing the stitches as close together as you can. Make sure that the two ends match up neatly.
Begin trimming the fabric by cutting slits, first from the middle to the top, then to the bottom, and then to each side to make flaps.
Fold the flaps to the reverse side. You can cut more slips to make smaller flaps in order to fold along the flaps more closely to the stitched line.
Take the embroidery out of the frame and turn it to the reverse side. Trim away the folded flaps up to the edge of the buttonhole stitch.
Structure of stitch
Cutwork removes part of the fabric, allowing any backing material to show through. Buttonhole stitch is a traditional stitch used for cutwork, and is the easiest way to get a neat finish because the stitch forms a corded edge. Stranded cotton and coton à broder work well for cutwork stitches.
Common uses
This method trims the fabric after completing the buttonhole stitch around the shape, so works well for larger and more complex shapes. This method can also be used with satin stitch or trailing, as well as buttonhole stitch as in the instructions.
The stitching may be worked at the same time as other core stitches, but the cutting away should be done at the very end.
Related Stitches
References
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Various Authors, The Royal School of Needlework Book of Embroidery (2018) , p.344