You show a rectangular frame with differently shaped blocks inside. The blocks fit perfectly in the frame. You remove the frame away, mix up the blocks and then recreate the rectangular shape. Now you remove another block from your pocket and add it to the rectangle. And then a second block is removed from your pocket, and this block is also added to the rectangle. You’ll amaze everyone when you pick up the frame and place it on the newly formed rectangle… and it fits perfectly! Wait till you see the puzzled look on their faces!
Even when you know the secret, you’ll still be puzzled!
Very easy to do.