Fig. 3. Left: A blacksmith's or stonemason's sledge hammer. Right: A jeweller's or watchmaker's hammer. Look at the action of the tool: If it saws, it is for hard material – wood, ivory, sheet metal. The finer the teeth, the harder the material, so a very fine toothed saw is likely to be for metal work. Fig. 4. Left: A keyhole saw for wood.