The smithies are small structures with grass roofs, but no sides or floors (Plate LXII). At one end is a raised bamboo bench in front of which stands the forge. This consists of two upright wooden cylinders, usually logs hollowed out, known as _po-opan._ In each of these is a piston or plunger (_doeydoyog_) at the lower end of which is a wooden ring packed with corn husks and chicken feathers. When this is pushed downward in the cylinder, it compresses the air and forces it out of the small opening in the base, but when it is drawn up, the packing collapses and allows the plunger to be raised without effort. These pistons are worked so that one is rising, while the other is falling. The cylinders stand in a wooden block out of which bamboo tubes (_toloñgon_) conduct the air into a tube of fire clay (_ibong_), and this in turn carries it into the charcoal fire. There are no valves, as in the Chinese bellows, but the bamboo tubes fit loosely, and the fire is not drawn back. Near to the hearth is a stone anvil (_dalisdisan_), while a heavy stone hammer, a small iron hammer, and iron pinchers complete the outfit. The fire is lighted, and the operator sitting on the bench alternately raises and lowers the plungers in the cylinders until the fire burns brightly; then the smith puts metal into the coals and allows it to remain until it reaches a white heat. It is then removed and placed on the anvil, where his helper beats it out with the large hammer. This is a stone weighing twenty or more pounds, fitted inside the handles so that it can be used with both hands. As a rule, it is swung between the legs, and is allowed to strike the metal as it descends, but some of the men raise it above the shoulder and strike a much more powerful blow. If two pieces of metal are to be welded together, as is often the case when broken caldrons are used, they are laid, one overlapping the other, and are held together with damp fire-clay. In this condition they are placed in the fire and heated, and are then beaten together. It often takes several firings to bring about a perfect weld. After the initial shaping, the smith completes the work with the small hammer, and the blade is ready for tempering. A bamboo tube of water is placed near by, and the blade is again inserted in the fire and brought to a white heat. Then the smith withdraws it and watches it intently until the white tone begins to turn to a greenish-yellow, when he plunges it into the water. The tempered blade is now smoothed down with sandstone, and is whetted to a keen edge. Head-axes, spear-heads, adzes, a few knives, and the metal ends for the spear-shafts are the principal products of the forge. The blades are by no means of equal temper or perfection, but the smiths of the Tinguian-Kalinga border villages seldom turn out poor weapons, and as a result, their spears and head-axes have a wide distribution over northwestern Luzon.