This HOWTO contains step-by-step instructions for turning a latent fingerprint on the side of a glass or similar into a latex fingerprint you can wear on your fingertip in order to fool biometric sensors.
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)