I don't get it with shark teeth. It seems like they will remain for a while around areas that aren't sat in or trafficked in carpet and upholstery, and in the areas that are used they quickly disappear creating a weird look. I did shark teeth in carpet once when I started, took a picture, and have never done it since. Customers like what we do, and I'm not pissing around trying to maintain some kind of consistent geometry while I am cleaning, or worse going over areas multiple times for the sake of vanity. Clean it, groom it, moving on...