What it is...
Dan got it. As for what it has to do with PCBs, well, not a whole lot except that my desk was all messy that day so I was using the carpet as a backdrop to photograph a pc board.
Yes. I know. It's a trick question, and not all that interesting in the end, but I was suffering from lack of sleep that day. I thought it just looked cool and so it seemed like a good idea at the time.