This is a metric hole test pattern that I developed years ago when I was doing more work with Shapeways. It is a flat, 3 millimeter thick piece with standard metric drill bit size holes, and can be used just as a decoration, or to measure detail, accuracy, and distortion (holes and flatness) in printed materials. It's also useful for judging the printed sizes of clearance or tap holes, or choosing a hole size to match a part you already have. The holes range in size from 1mm to 3mm in 0.1mm steps, and from 3mm to 10mm in both 0.1mm steps and 0.25mm steps. The holes are arranged in such a way as to require as little material as possible, and this was actually a bit of a challenge. After struggling with the math for quite a while, I ended up using a physics simulation library for the ideal placement. I think the result is quite pleasing to the eye. There is a cleaner key available on my blog site here: http://www.thefrankes.com/wp/?p=21001) Print. 2) Admire. 3) Smile. 4) Extra credit: Print another one and give it as a gift to someone you love. Be sure to include a mysterious yet strangely enticing note that emphasizes the object's worldly significance.The holes are organized in ââ?¬Å?rowsââ?¬Â and placed as efficiently as possible in order to limit material use. This results in a unique and beautiful shape. There are also small bumps on the edges to indicate the odd (x.25 and x.75) measurements. There is a cleaner key available on my blog site here: http://www.thefrankes.com/wp/?p=2100 (For some reason it didn't upload well here.) You can find it on Shapeways here: http://www.shapeways.com/model/125875/metric_hole_test_pattern.htmlIf you're really smart and up for a challenge, see if you can figure out a way using straight math to place all these circles so that they cover the smallest area possible, while still presenting them in an organized way.