Hexagon Cube - Wooden Puzzle Brain Teaser

The Hexagon Cube is an unusual cube puzzle is a cluster of 6 wooden blocks. 
When assembled, each face of the cube creates an Hexagon shape.
This brain teaser is made by careful carving two of the surfaces of each block, so that the individual pieces can interlock.
Even if you know the shape of the blocks, you will find that reassembling the cluster can be a very puzzling problem to tackle.