Broke down and got one of those tools, impressioned a Dexter/Schlage lock with it. Compared to using Vise Grips it went faster. The marks are very easy to see. Tried to take a picture of them, but my phone camera was not up to it. Compared to my home-made contraption it works better, for one thing where the key is attached is adjustable so it is easier to work with keys of different lengths between bows and shoulders.

Here is another view of it. Overall it is fairly well made, but the spring is not well secured and when I used it for a second lock it popped loose a couple of times. I need to do something to secure it so it does not fly away for good.

And the opposite side.

An advantage is that it does not leave a mark on the cylinder--in the past I have left marks on cylinders from the shoulder of the key hitting it when rocking the blank up and down, this cylinder did not show any marks.
