A net is an openwork pattern of cords, loosely woven and knotted, and used to catch fish and game. In medieval heraldry, “net” is also a canting term for a fret, or a fretty field. In Society heraldry, the typical net seems to be a fisherman’s net, as in the illustration.
There is also a Society example of a “herring net”, mounted on a long handle; the illustration is based on a woodcut in Olaus Magnus’ History of the Nordic People, 1555. Though both of these nets are period artifacts, we’ve no examples of either as a charge in period armory. See also spiderweb.
The Order of the Golden Seine, of the Barony of Illiton, bears: Azure, a rectangular net Or, in its dexter chief corner a plate.
Kwellend-Njal Kolskeggsson bears as a badge: A net Or.
Ailikn Olafsdottir bears: Vert, a hare rampant maintaining a herring net and a chief wavy argent.