Toy Block Door
From the Super Mario Wiki
The Toy Block Door is an object in the Game Boy Advance game Wario Land 4. The Toy Block Door only appears in the level Toy Block Tower, which is the first level of the Topaz Passage. It's locked; Wario would need to throw a Triangle Toy Block at the slot on top of the door to open it. It will lead to the next room of the level.