A wooden box is shown to your spectator(s).
On top of the box is a small, round glass window. Your spectators can clearly see through the window and inside the wooden box.
You hand the box to your spectators and ask them to look inside and try to open the mysterious box.
They will find it is totally impossible to open the box because it is completely sealed.

Next, you borrow a bank note, bill, or any other small object.
You then place the box and object behind your back (or under a table, under a napkin, etc.), and within the blink of an eye, the object is in INSIDE the box!

You hand the box out once again. No matter how hard they try, they cannot open the box!

Very easy to do once you know the secret. Lots of fun to perform!