When I first got the mechanical assembly puzzle (http://www.spacecubes.com/more.php?FORMAT=2d), I doubted its (unassisted) feasibility. Having lost all my copies, I sank about $65 into some plumbing supplies and a circular saw, with marginal success: (http://gosper.org/spacecube.jpg). With handheld tools and work, the circular concavities are so imprecise that the pieces are not interchangeable, and the thing collapses if you breath on it. But with greater precision (e.g., a bleepload of filing and tweaking) it promises a modicum of stiffness and a drench of difficulty. Due to the square vs rectangular design, there are no slippery little flats which seem critical to solving the commercial version. I can do this one on a tablecloth or rug or with a bunch of books for scaffolding, but can't imagine doing it on a smooth surface or no surface, which might make fun for two people. (Thanks Marian Aiken and Charlie Perumattan for the loan of your powerdrills.) --rwg