It really depends on your industry and level of sophistication.

Two hundred years ago, a millwright was a man who could design and build a water flume, a water wheel, a line shaft, and belting, and who could assemble the grist wheels or hammer or saw as needed. He could then maintain the whole thing. As industry evolved, he became a mechanic, a welder, an electrician, a machinists, a steamfitter, and today an electronics tech. But, essentially, he (now she also) can assemble and maintain a large industrial process.