I cut off little pieces and stick them to a piece of hard board, and use them to dress plane irons and chisels that actually have nicks in the edges.  It's a little coarse for sharpening, but it's good for removing material to get the backs of  plane irons and chisels flat, establish the bevel, get them square across, and get them ready for sharpening.  I have rehabilitated tools that I had quit using.