Only the correct piece of the puzzle can be pulled out of the knot, and then you have a problem faster than you want. The remaining parts slide apart. The real challenge begins when you try to reassemble the knot... A classic burr puzzle designed by Vesa Timonen.
In this game, very old joining techniques for wooden beams, numerous to be found in old houses in the roof structure, were used. Simple in design, it is secure when the connection is "closed".