Set the box on its side and stand on it for a height boost? Then check the higher-up areas of the walls now that you're taller
Mr. Stick places the metal box vertically, but...

Mr. Stick will tell you a secret...
He's kinda afraid of heights and falling from height. And vertically placed box looks very unsafe to stand on it!
He still can place it horizontally and stand on it though. But in this case:
- It will not grant too much height
- He's not sure if there's something hidden in the walls or ceiling. Or did you notice some suspicious place that he should check? If so, then can you show this place to mr. Stick?
And for the last: mr. Stick is still sure that he already checked everything, and now he just need to find a way to open the box with items or objects that already are in his possession.