Joe, the head repair man for a factory retired after nearly 40 years with the company. He had passed all his knowledge on to his crew.
However, 6 months after he left, a critical machine stopped working correctly and no one could figure out what was wrong. It was to big and expensive to start randomly replacing parts.
They finally called Joe, got him to leave his fishing hole and come in. He asked everyone what they thought the problem was. He spent a long time just looking a the machine. He had them turn it on and he put his hands on the side and stood there with his eyes closed for a few minutes.
Pulling a piece of chalk out of a pocket, walked over to a small sub-module and placed a X on it. "This is what needs replacing." and left.
Not really believing it, because the sub-module had NOTHING to do with the problem, they replaced it anyway because it was cheap and easy.
Low and behold, the machine was working perfectly again.
A week later they received a bill from Joe for $50,000.
The CEO was angry. "He was here for only a 30 minutes. I refuse to pay. Ask him for a detailed invoice."
Another week passes...
And they get the invoice from Joe:
Knowing where to put X: $49,999
They paid up.
The moral? There is knowledge and there is knowing.
I've seen this action myself.
In the semi-dark ages of big iron computers, when they came in a series of closet sized cabinets, I worked on a system where one of the cabinets opened up to show row after row of lights. (Like in movies in the 60s & 70s.) The old timers could sit down and watch the lights blink. After a few minutes they could say "There is a problem in cabinet 5, 3rd shelf, slot 2-5..."
I learned what the individual lights meant, but never had a chance to learn how to read them.