Wide and Long Puzzle
This optical illusion has appeared in various books in recent years, but here it is as a wooden hand made demonstration!
The puzzle shows two boxes, one of which appears to be long and thin, the other is shorter and wider. Yet when you swap them round, they turn out to be the same size. The paper versions encouraged you to cut the puzzle out to allow you to swap the pieces around. Here, as a wooden puzzle, you can simply pop the two wooden pieces out and swap them around very easily.
This should fool most of the people you show it to!
Made in the EU