It was only a matter of time before the brilliant minds at Tenyo came out with a new finger chopping effect. Oh No is just that effect and not only does the scissors cut a finger or pen in half, the two halves are then separated about a 1/2" or so.
This is strictly a quick hit closeup effect. The angles are critical in Oh No more than most tricks. The trouble with Oh No is that the illusions only looks good from certain angles. This is why you should experiment with this effect, learn just where your hand needs to be in relationship to the spectators eyes because if you don't, the spectator might not understand the effect.
Another thing to be aware of is that if you use this as a finger chopper, hopefully your fingers are longer than mine. My fingers barely fit through to the other side when the separation occurs (I do have short fingers). An alternative presentation would be to use a borrowed pen if your fingers are too short (however the borrowed pen takes the scary aspect out of the effect).
Then angle issue isn't that bad once you know the limitations so don't let that scare you off. Also, do not leave your finger in the severed position for too long, let them see it, gasp, then restore it - Done (I did it twice in the video so that you know that it is repeatable and that it requires little to no setup). The prop does look a little like a dark ages torture device, I wish they would have made it look more aged but alas it would not be a Tenyo prop then.
Another thing I like about Oh No is the price. To be honest in the last few years Tenyo products have become extremely expensive. This effect falls into the classic Tenyo line where you do get a lot for your money so you might want to keep that in mind.
This is a strange looking device that will make your audience believe that solid can pass through solid. A pencil, or even your finger is placed into the box, and the built-in scissors cut right through. This illusion is wonderful, and is as safe as can be, as the blade never comes near your finger.