Fuller (groove)

[citation needed] When impressed during forging, it may be made using a blacksmithing tool that is also called a fuller, a form of spring swage.

The ridges and groove created by the fuller are comparable to an I-beam's flanges and web; this shape aims to optimize the strength and stiffness for a given quantity of material, particularly in the cutting direction.

[3][4][5] The term "fuller" is from the Middle English fuliere, meaning 'one that fulls [pleats] cloth'.

If a groove is to be applied to both sides of the steel, two fullers may be used at the same time, sandwiching the workpiece in the middle.

In addition to being used to "draw out" steel, hammering a short block into a long bar, fullers are also used in the production of items such as hinges and latches, plow parts, and horseshoes.

Partially fullered blade of a USMC Ka-Bar fighting knife
In bladesmithing, fullers are often used in pairs. The upper fuller has a flat surface for striking with a hammer, while the lower fuller has a square peg that fits into the anvil. The fullers displace material in the blade, causing it to move sideways and bulge outward from the surface.
The heavy-bladed traditional Nepali kukri may have a fuller, or a hollow ground bevel