My dad was a machinist and had tri-focals, or double-bifocals. His glasses had distance in the center portion, then a reading strength at the top and another at the bottom of his lenses. Bottom portion was for reading the machine handles and seeing the parts up close, top portion was for reading the digital display and electronic gear sitting on top of the machinery, middle portion was for general looking around. And, yep, he had to go to a couple of places before finding someone to do what he needed.