柄の木と嵌合

The handle is porous, replaceable, and sometimes handed

A Japanese handle is friction-fitted rather than bolted on, which is why it can be replaced — and why it is porous in a way a Western handle is not. One common shape is also ground for one hand.

Two different ways to attach a handle

Wikipedia describes the construction directly. Japanese handles are traditionally made of ho wood, burned in and friction-fitted to a hidden tang; the wood is porous and fine-grained, which makes it less likely to split and helps it retain grip. A metal collar or buffalo horn bolster caps the handle-blade junction and further reduces splitting, and the whole arrangement allows easy installation and replacement. Western handles are the opposite construction: a bolster with a full or partial tang, and scale materials that are often synthetic or resin-cured engineered wood, and non-porous.

Porous is the word to sit with, because it explains the care. A wa handle absorbs water, so it is not a part to leave soaking, put through a dishwasher or store damp. The trade is what the source gives on the other side: friction-fitted handles are easy to replace, so a wa handle is a consumable part of the knife rather than a permanent one. A Western handle asks less of you and cannot be swapped in the same way.

The woods, and which ones crack

Decorative woods behave differently again. Ebony, yew, cherry and chestnut are used, are heavier, and are often charred on the outside to improve grip and water resistance — and the source is blunt about the risk: if they are not cured well or properly cared for, these woods crack more easily when exposed to moisture. Pakka wood, laminated wood in a synthetic resin matrix, is the opposite choice: not porous, waterproof, less likely to split, and used on less expensive knives.

Where to look

Listings usually name the handle wood and stop there. Two things are worth finding beyond the name. The shape in cross-section, because a D-shaped handle is made for one hand and an octagonal one is not — and if you are buying a single-bevel knife, that is the second place handedness appears. And whether it is real wood or a resin composite, since pakka wood asks nothing of you and ho wood asks to be kept dry.

No shop link here. A handle is not usually bought separately unless you are replacing one, and if you are, the fit is specific to the knife. What this page can give you is the reason replacement is possible at all: the handle was friction-fitted, not bonded.