BellaBoo has that right!
It works like any other long wide ruler.
It works like any 45 degree triangle ruler.
It works for any 30/45/60/90 degree cuts.
It works like an 8" square ruler.
It makes a mean mitered border ruler....was with this one "way back when" that I taught myself to miter!
It was "the bomb!" in it's day. No reason to replace those wonderful, well thought out original tools, just because there are so many new quilters making so many new gizmos these days. I'd rather have one good, I-know-how-to-use-this tool any day than a bunch of new what-was-this-for?? tools cluttering up my space any day!
Jan in VA