Die Tunnel

You show a rectangular tube and a die that just fits into the tube. You show that the die cannot turn on its side once in the tube since there is no space in the tube for the die to turn. You pass the die through the tube a couple of days to prove your point. Yet when you say the magic word the turn mysteriously turns itself inside the tube.

This is a very easy to do and inexpensive trick that can be repeated instantly.