Just bought a 3930 and also bought a scraper thing that I thought was a box blade but it doesn't have sides on it. The attachment has ripper teeth and also a scraper blade. It has a third blade that I'm not sure what it is for. The attachment has a handle on top that you can pull and when you do the blades swivel like a guillotine. Not sure what I bought. Hopefully, I can use it for something.