[ He frowns and lifts his hands. ]

I don't know what they're made out of. But my powers only work on metal, and not all metal is affected the same way.

[ And certain very rare minerals but that's besides the point. ]

Certain metals, like aluminum or copper, have such a negligible response that it's rarely worth the effort to not simply manipulate them manually. And if the door is made of ceramic, plastic, glass, stone? It's even worse. With the right materials I can achieve nearly anything but with inert substances it's a waste of time.