Boning is used to stiffen the bodice of dresses. Like in the period costumes of 1800's. I used it several years ago when I made bridesmaid dresses. You sew a casing then insert the boning to hold the dress stiff and hold its shape. It is plactic strips in a cloth casing. At the time I used it, it was very inexpensive, dont know about now. It was sold by the yard. Good luck.