I don’t find that splitting the fatwood works well for catching sparks from a fero rod. Even splitting the fatwood fine, it is harder to light using sparks. What works best for me is to hold a knife at a steep angle to the lighter wood and scrape fine shavings off with the edge. I end up with something that looks more like the shavings from a carpenter’s plain than little match sticks. That shaved fatwood catches fire without a struggle.