What is Marumune in Japanese Katana terminology?

The term "Marumune" (丸棟, まるむね) refers to a type of ridge on a Japanese sword that has a semi-circular cross-section. This unique shape is often seen in swords from the old Oshu and Kyushu regions. It is also known as "Sounomune" (草の棟). The ridge of a sword is an important feature that contributes to its overall structure and balance. The Marumune style is characterized by its rounded, semi-circular shape, which distinguishes it from other ridge styles.