Making Celtic Knotwork

I found this tutorial on creating Celtic Knotwork, a technique that could be effective in creating some beautiful patterns.

Web page here.

This technique could be effective in adding adornment to medieval designs, or simply in creating patterned backgrounds and fillers. I am considering using a similar sort of artwork in one of my typography pieces.

The page also has links to the purchase of a font, that creates not lettering at all but simply variations of the patterns. It would be much more satisfying however to create all the artwork from scratch.