If an engineer wanted to construct a shiv while in prison, how would they go about it? Assume they had sophisticated knowledge, but no tools (other than having a bit of metal available)
  1. find some sandstone
  2. make the stones flat by rubbing them together
  3. sharpen the shiv the against the stone
  4. if you want to make it extremely sharp, progressively move on to siltstone, claystone, and maybe a strop