Cubic Lock

These are the four pieces of Cubic Lock by Goh Pit Khiam as realized in exotic woods by Brian Menold. A union of the two pieces on the left (top, the key made up of 10 cubies; bottom, 9 cubies) is inserted into a union of the two pieces on the right (top, 23 cubies; bottom, 19 cubies) and by means of a strategic to-and-fro of the key, the pieces are shifted into place. It's not obvious that the finished 4*4*4 cube has an internal void until one counts and adds those cubies. A good show-off puzzle as one is unlikely to forget the assembly once one has put it together a few times.