The quaternary knot symbol could depict or indicate four directions (East, West, North and South). The symbol could also mean four elements of nature i.e. Earth, Fire, Water and Air. The fire festivals of Celts i.e. Samhain, Beltane, Imbolc and Lughnasadh could also be an interpretation of the quaternary symbol.
Celtic farmstead in North Wales, dating to the 3rd century AD. The family is preparing for the winter: you can see smoke rising from chimney holes as women cure meat, men carrying pigs that will be fattened for slaughter, a man winnowing wheat and barley (throwing it up into the air to get rid of the chaff, the part you can't eat), a small hut to store logs for winter fires, and men fixing a barn for storing hay for the cattle.