The goal is to get an exact image of the fingerprint, for further use as mold, out of which the dummy is made. The easiest way is to print the image on a transparency slide (the ones normally used for an overhead projector) with a laser printer. The toner forms a relief, which is later used similar to letter press printing. Wood glue is suitable for producing the dummyLink (via Kottke)
I write books. My latest is a YA science fiction novel called Homeland (it's the sequel to Little Brother). More books: Rapture of the Nerds (a novel, with Charlie Stross); With a Little Help (short stories); and The Great Big Beautiful Tomorrow (novella and nonfic). I speak all over the place and I tweet and tumble, too.