As an experiment, I've uploaded a PDF of "Six Screws for Seven Spokes" to GoogleDocs at (no linebreaks; just trips of the tongue, don't it?) https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid=0B6QR93hqu... I'd appreciate it if somebody would let me know whether this can (as promised) be downloaded directly from this link by Joe Public --- and even more if I can have some feedback about the content! Jon Selig tells me that the theory is familiar among the robotics community, having been developed 20+ years ago in the somewhat different context of the number of fingers required by a mechanical hand --- imagine trying to grasp securely a light, slippery ball, without it touching the palm. With one hand --- could be a good game for party forfeits in there! The reference he gives is B. Mishra, J. T. Schwartz and M. Sharir, "On the existence and synthesis of multifinger positive grips", Algorithmica, Volume 2, Numbers 4, 541-558 (1987) Fred Lunnon