Blade Grooves in Japanese Swords: Bo-hi, Futasuji-hi, Koshi-hi, and Kakinage-shi — Classification and Appreciation

Japanese Sword Grooves (Hi) - Main Elements

The blade of a Japanese sword has decorative carvings made by hand, in addition to notable aspects of the steel itself such as hamon and jihada. Among these, the most common is a groove called "hi." Hi is not merely ornamental but is incorporated as an important structural component within the form, and is classified into several types based on its shape.

The Role and Basics of Hi

Hi is a fine, elongated groove carved along areas such as the shinogi-ji of the blade. It is often described as "a groove for weight reduction," but this is not its only purpose. It also has significant sculptural meaning in tightening the overall form and adding variation to the expression of the blade. By carving hi, the weight distribution changes, which also affects the sensation when wielding the sword.

Hi is classified in detail based on the number of grooves, their position, length, and how the end of the groove is finished. Below are representative shapes.

Main Types by Shape

• Bou-hi: The most common type of hi, carved as a single groove along the blade. A clean, single groove imparts a straight, powerful quality to the blade. When people think of hi, most first imagine this bou-hi.
• Futasuji-hi: Two thin grooves of equal thickness are carved in parallel. The paired style is said to be intended to represent the ritual sticks (gomabashi) held by Fudo Myoo, and sometimes carries religious significance.
• Koshi-hi: A groove carved short on the lower part of the blade (near the hilt). Rather than running along the entire blade, it is used to tighten the area near the base of the blade.

Beyond these, numerous variations exist such as shobu-hi, tsure-hi, and others, depending on the region, period, and the preferences of individual sword makers.

Soe-hi and Carvings Within Hi

When a thin groove is carved alongside a bou-hi, it is called soe-hi. The contrast between the thick and thin grooves imparts a rhythmic quality to the form. The naginata-hi seen on blades of naginata straighteners typically features a groove carved short near the point with an accompanying soe-hi, and is noted as an observation that speaks to the history of the blade. Furthermore, hi is not only carved independently but is also combined with techniques that create carvings such as Sanskrit characters or simple swords within the groove itself, showing the close relationship between hi and sword blade sculpture. While the carvings themselves belong to a different classification than hi, in that both involve inscribing faith and prayer onto the blade, they exist on a continuum with the religious implications of hi such as the gomabashi of futasuji-hi.

The Pitfall of "Ato-hi"

When observing hi, it is important to understand the distinction between hi carved from the time of manufacture (nama-bu hi) and hi carved in later periods (ato-hi). Ato-hi may be carved to make a blade that has worn from polishing appear lighter, or to make forging flaws and damage less noticeable, and is a point of particular concern when considering a purchase. The following perspectives serve as guides for judgment:

• Whether the position or depth of the hi is unnaturally out of proportion with the overall form
• Whether the jihada within the hi is consistent with that in other parts of the blade
• Whether there are any contradictions in the relationship with the suriage

Since definitive judgment is not always easy, when in doubt, it is prudent to consult the opinions of trusted sword dealers or examination organizations.

Points of Care in Maintenance Regarding Hi

When maintaining a blade with hi, a little attention should be paid. Oil tends to accumulate in the groove, and if not wiped thoroughly, it can cause oxidation of the oil or rust. When using uchiko or wiping paper, confirm that the area is wiped evenly not only on flat surfaces but also within the hi. Additionally, the edge of the hi is a part where the standing changes through polishing, and whether the hi has become shallower due to years of polishing or whether the edge line has sagged provides material for assessing preservation condition.

Differences in Finish at the End of Hi

Hi is also classified by how the end of the groove, called the hi-jiri, is finished.

• Kaki-nagashi: The hi is carved to flow through the middle of the nakago, with the end gradually thinning without a clear stop.
• Kaki-tooshi: The hi is carved to pass through to the tip of the nakago.

Differences such as whether the hi-jiri ends in a round or angular manner also serve as subjects of observation as characteristics of the sword maker and period.

These terminal treatments can reflect the hand habits and school practices of the carving craftsman, and are details not to be overlooked in appreciation.

Observation Points in Appreciation

When viewing hi, the following order of observation is recommended:

1. First, confirm the number and position of the grooves, ascertaining whether it is bou-hi or futasuji-hi, and whether the groove runs the full length of the blade or only near the hilt.
2. Next, move your eye to the hi-jiri and trace whether it flows and fades away or runs through to the nakago.
3. Furthermore, whether the hi is carved cleanly in alignment, and whether the depth and width are consistent, also serve as material for judging the quality of the work.

Also, when observing hi in photographs, images taken at an angle to the blade make it easier to understand the depth of the groove and the way the edge stands. Images from the front alone make it difficult to assess the precision of the carving, so it is recommended to compare images from multiple angles. Additionally, the presence or absence of hi is not uniform even among works by the same sword maker and varies depending on the commission or intended use, so the absence of hi does not necessarily indicate lower quality. The proper approach is to evaluate based on harmony with the form and the quality of the carving.

Hi is the most approachable element of sword blade sculpture and greatly influences the impression of the blade's form. This site presents listed swords with blade images in our online catalog, which can be utilized as an entry point for comparing the presence or absence of hi and its shape through images.