First, let it be said that I don't really make bound buttonholes. I did it on one dress (with a limp rayon challis that easily frayed) and decided I didn't care if I ever did it again. But as with almost any vintage Singer doo-dad, I'm willing to try it just for the novelty factor.
This kit consists mainly of three things to "help" you make a bound buttonhole - any of which you could do just as well without:
1. Pattern templates that you actually pin to the fabric and sew over to get your buttonhole exactly right. You could draw or download your own, of course.
2. Step-by-step instructions. You can find those anywhere
3. A flat metal tool that you use to press the folds that make the buttonhole opening. You could press without it, this just makes it sharper.
Since this was an unused vintage item, I made copies of the pattern templates so I won't have to destroy the originals.
They come in sizes from 3/4" to 1-1/2". I chose the 1-1/4" for my test sample