Closed Button Hole Stitch is a variation of button hole stitch. It can be used to embroider pretty borders and also used as an edge stitch.
This stitch is worked between two parallel lines.
Bring the needle up at A. Go down at B and come back up at C. C is close to A. The working thread will be below the needle.
Pull the thread and needle through and the stitch will look like this.
Go back and take the needle down at B and bring it back up at D.
The first triangle has been made.
Repeat the steps
Finished work will look like this.