OK, I'll try to describe it!
You know the paper templates that you can buy/print out that you layer your two fabrics right sides together, put the paper on top, and then start at one corner, and by turning right and left, in a continuous line of stitching, make HSTs? It kind of looks like you've stitched double lines making squares on point on the paper, but when you cut on the lines, you have all these perfect little half-square triangles.
Well, this was a digitized embroidery design that did this in the hoop--you hooped the fabrics together, and it stitched away, and when it was done, you cut them out and had them all nice and neat.
I figured I could get a lot of them done, then work on piecing them together for the design. Not sure what size the HSTs would be, or if there were different patterns for them.
If I hear of who has them, I'll be sure to post it--because it would work on any embroidery machine, I believe.