A fuller is the groove running down the flat of a blade. It is not a blood groove and it does not exist to let blood out or air in, both of which are stories invented long after the fact. A fuller removes steel from the middle of the blade, where it contributes least to stiffness, and leaves the material at the edges where it does the work.
The engineering, briefly
The same principle as an I beam. A blade resists bending mostly through the material furthest from its center, so metal in the middle is almost dead weight. Take it out and you drop mass without a meaningful loss of stiffness, which moves the balance point back toward the hand and makes the sword turn faster. On a long blade that difference is the whole handling character of the piece. A forged fuller is worked into the steel, which also refines the grain along its length. A milled one is cut out afterwards and is a different and inferior thing.
What is on this tag
Arming swords at 38 inches overall with blued fullered blades and wheel pommels, scimitars at 37 inches with 31 inch blades, fencing swords at 39.5 inches with 32.5 inch blades, side swords at 39 inches with 32 inch blades, and Viking patterns. Steel is plain 1095 high carbon at 54 to 58 HRC or Damascus of 1095 and 15N20, forge welded and acid etched, at 58 to 60 HRC. Several carry etched knotwork bands inside the fuller itself.
What to look at
A good fuller runs true down the center and stops cleanly before the point rather than running off the end. It should be even in depth along its length. If the terms around all this are unfamiliar, the display against battle ready explainer defines what the market means by them. The single hand shapes are in the arming swords, the single edged medieval blades in the messers and the curved ones in the falchions.
Fullers on curved blades
Scimitars, sabres and falchions carry fullers too, usually running close to the spine rather than down the center, because the mass distribution on a curved single edged blade is a different problem. On those the fuller is doing the same job of removing dead weight, just from a different place, and it often stops much earlier along the blade.
Free US shipping
On most pieces. Heavier and oversized ones carry a flat charge.
Hand Forged
Heated, hammered and ground by hand.
Engraving available
Names, dates or Norse runes on most pieces.
