In my sh I haven't ever used blades. I often think about them, but I'm scared to cross that line. My sh is blunt force. I hit my head. I used to use my fists, but I typically go for walls now. After some time I've become sensitive to the quality of the wall. The last time it was cement wall with a laminated covering. I find I fantasize about using a hammer, but I'm scared.
Regarding blades, I have a very sharp small Japanese kitchen knife that I rare use. I sometimes hold it, close to cutting, but I haven't yet.
My first ctb attempt was when I was 16 and tried to cut myself with a flat double edged razor. I skimmed the surface, but couldn't commit. This makes me feel I still couldn't, but I have the craving.