It's missing a part. There is supposed to be a small hook (90* that is) on the end of one leg. Without it the jig could be dangerous to use. I can post a pick of one with the hook if you want to see it. As stated, they can be handy. I don't use it often but enough to justify what I paid for it many years ago.
Actually it's missing two parts. The other part is the handle you push it with.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.