There are two goals to the Cast Nutcase created by the Dutch puzzle inventor, Oskar: 1. Remove the small nut by disassembleing the cast nutcase. 2. Cast puzzle enthusiasts (nutcases) can enjoy trying to change the wording on the bolt from 'nut-case' to 'case-nut'. The key word is "Interlocking." Another great metal puzzle puzzle from the Hanayama Cast puzzles.