The Caged Block Puzzle Box by Bill Sheckels is a hybrid puzzle combining an interlocking burr with a secret opening mechanism. A central Walnut cube sits trapped inside a cage of eight interlocked Ash sticks — the exterior gives no obvious hint of where to begin. Once you find the hidden move that releases the cage, you disassemble the burr sticks to free the cube, which then opens to reveal a storage compartment inside. A satisfying two-stage sequential discovery that looks deceptively simple...