Abstract: A pressed crease-forming member includes a strip-shaped member having a crease-forming portion formed with three or a larger-than-three odd number of ribs extending in the longitudinal direction of the strip-shaped member with one of the ribs located at the widthwise center of the crease-forming portion and each half of the remaining even number of ribs arranged on either side of the center rib. At least the top of the center rib, namely, the rib located at the widthwise center of the crease-forming portion, is chamfered. Grooves are formed between the adjacent ribs. The ribs are arranged such that the tops of the ribs are formed, as a whole, into a convex shape. The bottom of each groove is recessed beyond the tops of the ribs on both sides of the groove.

Abstract: A pressed crease-forming member includes a strip-shaped member having a crease-forming portion formed with three or a larger-than-three odd number of ribs extending in the longitudinal direction of the strip-shaped member with one of the ribs located at the widthwise center of the crease-forming portion and each half of the remaining even number of ribs arranged on either side of the center rib. At least the top of the center rib, namely, the rib located at the widthwise center of the crease-forming portion, is chamfered. Grooves are formed between the adjacent ribs. The ribs are arranged such that the tops of the ribs are formed, as a whole, into a convex shape. The bottom of each groove is recessed beyond the tops of the ribs on both sides of the groove.