I use my turn screw. I hold my finger under the edge of the flint. putting the edge of the turn screw about 1/32 or less from the edge of the flint, then tap the turn screw. It takes just a little practice, then you will be able to drive off really small shards of flint, bringing the flint to a razor sharp edge. I for one can't do any thing with a knapping hammer. This can also be done with a nail with a step filed in or a piece of brass used as a punch. bjh