Artificial koma-nagura stone. The fifth stone of the groundwork; used before uchigumori-do to remove the marks left by Chu-nagura. If the polishing work is not done completely at this stage, and the marks left by Chu-nagura remain, it is difficult to achieve the effect of Uchigumori-do. The hamon has usually become clearly visible at this stage. Dimensions 18 x 5 x 5 cm, weight 860 g.