About ten years ago we came across a puzzle called Bank Raid, in Leonardo’s Mirror & Other Puzzles by Ivan Moscovich.
The puzzle itself was inspired by the 2- dimensional world of Flatland: A Romance of Many Dimensions by Edwin Abbott Abbott.
At the time we made a crochet blanket. Obviously it was not possible to physically move the pieces so it was just a reasoning puzzle.
I have now gone back to it to make a version where you can actually move the pieces.
The complete puzzle.
The lid is fixed to the base at the four corners. The sides of the frame are open for the pieces to slide out.
The four pieces of the lock can move up, down, left and right.
How do you remove all the pieces?
One of the photos below shows the complete shapes of the four pieces; the other shows what you see when the lid is not in place.
The video shows the solution