Idk what kind of blade you're talking about the little one wrapped in heavy paper around the blade? but they seem to brittle to bend, I've broken many of them just saying.Imagine the extreme sharp edge of the blade - "just the tip". Now imagine that whole edge, just the tiniest few thousandths of an inch, pushed slightly "sideways" after dragging it at a slant over the sandpaper. That's the burr I'm talking about. Now, if you bend the blade into a very slight U shape, so that the burr now is on the "outside" edge of the U, you can drag it over the run. Because of the curve shape, only a very small section of the blade will be in contact with the paint, and again because of that curve, the corners of the blade will stay safely up and away from the paint surface.