Spearing A Banknote - Leaving No Trace Of Damage

Many a time, I've inadvertently damaged a banknote in my haste to deprive myself of well-earned cash. But that was by accident. Here's a demonstration of a deliberate attempt to pierce a banknote with a sharp instrument. The magician shows a banknote and a simple sleeve made from a folded small sheet of paper. The note is folded in half and placed inside the sleeve. Both ends of the note are kept visible. A letter-opener is now inserted between the folds of the note and shown from all angles. The letter-opener is then pushed through both the note and the sleeve, leaving the point freely visible below the arrangement. The spear is then withdrawn. A hole is clearly seen in the sleeve, but the banknote is mysteriously untouched. I'll need to remember this one when next I half-destroy my legal tender.