Cardboard and Water Magic Trick

Amaze your friends with this easy magic trick.

-pocket knife
-cardboard
-water
-cup (in my opinion a clear glass works the best).
 

Cut the cardboard so it is a little bigger than the glass.

Fill the glass about 1/4 of the way full. Then place the cardboard on the top of the glass.

To start out put your hand on the cardboard and slowly tilt the glass upside down so that all of the water is sitting on the cardboard. Then slowly and carefully remove your hand off the cardboard. the cardboard should stay on the glass! Any sudden movements will cause the cardboard's seal  to fail resulting in a mess full of water.