One of my favorite projects in undergrad was making this puzzle box. I designed and manufactured (milled) an aluminum box with 8 interlocking parts. With carefully placed slots, I press-fit all the walls and the internal maze.
The moving face is constrained by the slots and walls of the box, but is still able to move freely along the path of the maze. What results is a box you can only open if you move the face or sliding piece in the right directions. When you solve the puzzle, you can slide off the lid.
Steps for removing puzzle box lid
Designing and manufacturing this puzzle box required planning the dimensions of the parts, prototyping the concept, producing drawings to reference while machining, and finally machining and press fitting the final product.
Jessica McCallum 