Yes, exactly. That mechanism must be non-obvious. My suggestion is that if I pose the problem meant to be solved to a random group of professionals and they quickly come up with the mechanism for solving it that an applicant is attempting to patent, then that mechanism is very likely obvious.

Take as an example the "Drinking Bird." Imagine the inventor has applied for a patent. You get some materials engineers and a physicist or something in a room, describe a device which resembles a bird and continuously sips water, and ask them to devise a way to build it in a few hours. If they describe a bulb full of dichloromethane with a tube leading up to a beak, then it's not patentable.