be steepened if employed for harder woods. . The kiri is used for boring circular holes in a timber, often as the first stage in the hollowing out of a mortise. Though seemingly simple to use, the kiri is commonly considered one of the most difficult tools to master. . The sumitsubo is used for marking long straight lines onto various surfaces. A thread (tsuboito) is tied to a rounded piece of wood with a needle fixed at the end (karuko). The other end of the thread is passed through the small opening at the end of the sumitsubo (itoguchi), through the depression containing ink (ike) and wound around a spool (itomaki-guruma). The ink is stored in the ike soaked in silk wadding. Silk threads are used as tsuboito. To draw a line, the sumitsubo is held in the left hand and the karuko's needle is fixed onto the surface determining the position of one end of the thread. The sumitsubo is gradually moved away from the karuko until the required length of the thread is unreeled at which point the rotation of the spool is stopped using the thumb. With the index finger the thread is pressed down at the required end point of the line. Using the right hand, the thread is pulled upwards into tension and then suddenly released, consequently hitting the surface and leaving a straight line of ink onto any surface, regardless of any surface irregularities. Japanese axe and adze ( and ). . There are several types of carpentry hammers. Some hammers are used for chisel work, some for positioning hand plane blades, some for hammering and pulling nails, and others for tapping out laminated hardened steel from base of plane blades and chisels. Tools for measuring and marking include the , , , the traditional single and multi-blade , among others. Blades Though a carpenter will typically fashion handles and woodblocks and set and sharpen their blades themselves, the blades themselves are forged by steel smiths and provided unmounted to the carpenter. Japanese steel has long enjoyed a high level of refinement, without which the fine surfaces and detail for which Japanese woodwork is renowned would not be possible. The blades used in the Japanese chisel and the Japanese plane shares similar constructive principles to the Japanese sword. A thin piece of extremely hard blade metal called is forge-welded to a softer piece