Demon close-up glass penetration

This high quality, Demon stamped, apparatus would give a professional magician years of trouble-free use. It consists of a piece of glass within a metal frame. The magician tucks a card into the frame, one card on each side of the glass. The magic begins when a pencil is pushed right through the centre of one card, through the glass and out through the centre of the card on the other side. Both cards end up with a hole through them, but the glass remains intact. The apparatus may be examined before and after the penetration but no solution to the mystery can be found.