a.k.a. Sneaky Squares, Stark Raving Cubes, Block Out, Square Fit, KUBI
Designed by Bill Cutler, wood version made by J. Devost, 1983.
(left: oak, 4.5 inches square by 2.25 inches high;
middle: Sneaky Squares / Start Raving Cubes, plastic, 4.5" square by 2" high;
right: Block Out / Square Fit, 3" square by 1.25" high)

Four pieces cut at odd angles (so that they not quite cubes) must be placed into the box (a three piece version has also been made). Inserting one at a time will not work. To solve, arrange them on the table so that the top is level and square, push them together at the bottoms, and drop them into the box. Here is what the pieces look like in their solved positions, outside the box: