The puzzle contains 4 pieces : 2 triangles and 2 trapezoids.
One frame is larger than the other. The larger frame is used to store the pieces.
Turn it over
Notice that this side is smaller and the frame is thicker.
Now, try to fit the 4 pieces in the frame.
* Do not use strength.
If you solve it correctly, the pieces will slide in to place smoothly.
An ancient puzzle attributed to the Greek mathematician Archimedes. There are a startlingly large number of ways to fit this puzzle together, see how many you can find.