With the eyes I have now doing a key "impression" is long gone but I used to do quite a few. You can do a search on impressing a key for a good explanation but it is basically using a soft brass key blank that you turn firmly with a small vise grip to imprint the tumblers onto the soft metal. You then file till every trace of the tumblers are gone to make a key that will work the lock and then read the tumblers position onto a key cutter to make a permanent key.
