wiki-Flat (Hira)

• Definition: The flat section of a Japanese knife blade, located between the ridge line (shinogi) and the cutting edge (kiriha).
• Details: The hira is typically smooth and even, forming the central portion of the blade’s geometry. It not only contributes to the knife’s structural integrity but also influences how smoothly the blade passes through ingredients.
  
• Comparison: Compared to the kiriha (cutting bevel), which directly forms the edge, the hira is broader and flat. While it does not cut directly, its flatness helps guide the blade and supports stable cutting performance.
  
• Practical Use: The hira can be used for light crushing of ingredients such as garlic or ginger. It also aids in precision cutting when working in tandem with the cutting edge or tip. Its role is particularly important in single-bevel Japanese knives like yanagiba or usuba, where blade geometry strongly affects performance.
  
• Related Parts: The shinogi (ridge line) separates the hira from the edge bevel, reducing resistance during slicing. The kissaki (tip) extends from the hira to allow for detailed, delicate cutting tasks.

Related websites
Parts of a Japanese Knife