I have had the Blockhead puzzle (designed by Bill Cutler) for over a year now. In fact I have three. One from Brian Menold, a plastic version from ThinkFun (marketed under the name "a-ha Square Fit") and the third I chanced upon at a local flea market; very cheap at $3/- but works.
Needless to say, the largest and best (and most expensive but value for money at only US$30/-) of the three in my collection is the version made by Brian. It's constructed from Yellowheart and Paduak. Very nice contrast of colourful woods here. Quality, fit and finish is very good and it even has fine Paduak detailing at the four corners of the frame.
The Blockhead has been around since 1983 and is generally considered a must-have classic. Over the years, it has been mass produced and marketed under different names. Its one of the most manufactured puzzles around, made by different puzzle craftsmen at different times.
It's a packing puzzle and the object is to fit four square blocks inside the box frame. At first glance, it seems really easy....but don't be deceived. What looks simple never usually is. And in this case, the square blocks are not really all that square either. Each block has its sides cut at an angle, making them more like 3D parallelograms. Even the insides of the box frame seem to be lop-sided! And fitting them all flush into the frame is no longer simple after all.
For the Blockhead, I already had some clues on how to go about solving it even before I got my copy, having watched someone else playing with it, so I had a head-start. But notwithstanding, I still fumbled for a while after taking out the pieces and causally scrambling them before re-arranging them correctly for insertion back into the frame. One block will always refuse to go in. I would have definitely taken much longer if I did not have any prior hints because it is a very challenging puzzle no less. And certainly one that is quite different from other more traditional packing puzzles. And too bad, Burr Tools won't help here!