Fuller (weapon)

A fuller is a tool used in the trade of blacksmithing to produce a rounded or beveled groove or slot in the flat side of a blade (e.g. a sword, knife, or bayonet), and it also refers to the grooves made by these tools. These grooves are often called "blood grooves" or "blood gutters" as well as fullers, although their purpose has nothing to do with blood. A fuller is often used to lighten the blade, much the way that the shape of an I-beam allows a given amount of strength to be achieved with less material. When combined with proper distal tapers, heat treatment and blade tempering, a fullered blade can be 20% to 35% lighter than a non-fullered blade without any sacrifice of strength or blade integrity. This effect lessens as the blade is reduced in length. This groove is often called a "fuller" by sword enthusiasts, but it is the tool used to make the groove which is actually a fuller and the blade is said to be "fullered" after introduction of the groove.