This is for a magic trick called puzzle paradox or block puzzle. The following youtube videos show how it is done. It can also be purchased from most magic trick store. http://www.youtube.com/watch?v=qCOoXrPmKkc http://www.youtube.com/watch?v=h-GKOHZc4bQ http://www.youtube.com/watch?v=QrTMxKkVt1c http://www.youtube.com/watch?v=vVeLI10f2q4 As you may see in the videos, there are some pieces are confusing and not interchangeable. I changed the dimensions so that b2 and b9 are exactly the same. However, although b4 and b6 look similar, they are actually different and cannot be interchangeable. ?????????? http://www.youtube.com/watch?v=F2b9bkBxUXs