A Guilloché pattern is a decorative engraving technique, according to Wikipedia. It’s been used in fancy documents such as paper money. But to most of us, it looks like what a Spirograph would create. The Guilloché Pattern Generator is an online generator that makes these patterns, designed by Tom Beddard. You can change the pattern by adjusting the parameters in the control panel on the left. Then press “s” to save your masterpieces. -via Metafilter