A guillotine with a very ingenious little finger!
Show the guillotine and pull out the blade. The latter is solid wood with just a hole in the centre. The base can be opened in two, and all parts (base and blade) can be shown.
A spectator introduces his finger into the hole in the base. You now place the wooden blade above ... The spectator presses himself on the blade that goes down and pierces his finger!
The base is now open in half so that the finger of the viewer who has passed through the hole of the blade can be seen. He pierced the blade !!!
The material is safe