When the piece of lumber was larger, is it just a matter of hitting away from your fingers. Once (the wood, not your fingers) are in smaller pieces, you place the edge of the blade where you want it, then lift both axe/hatchet and wood together, then bring them both down with enough force to imped the blade in the wood. Next whack, fingers are out of the way, wood gets split. You can do it when the wood is larger, altho it is not as easy then. Gloves and eye protection a real good idea too...
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OBG