Foley Belsaw lesson 7 instructs you how to impression a warded lock. I've gotten good at impressioning pin tumber american pad locks and have all the equipment to do so, including a key holder.
TIP: Do not use a key holder and put the bow of the key flush to the key holder for this lesson.
I did that first try got great marks, started like they said just a line accross the top and it marked again so I went ahead and cut, kept making great marks, but i ignored the marks near the tip, didnt' even see them till i went to test the key. I had about 1/4 inch of the key into the holder so it was not going all the way in....
Just a little friendly tip for that lesson.