I heard the same story when I was a kid, but it was about a boilermaker. The rest was for knowing where to tap his hammer to fix their problem.

It's an obviously apocryphal story with two great messages. First, don't undervalue your expertise just because the fix was easy (I still have a problem with that). Second, if you don't know what you're doing don't question the expert just because it looked easy.

It's a real story!

https://www.smithsonianmag.com/history/charles-proteus-steinmetz-the-wizard-of-schenectady-51912022/

At the beginning of the 20th century Henry Ford's electrical engineers had issues they could not solve with a gigantic generator. Henry Ford called Steimmetz, a genius mathematician working for GE to help them.

When he arrive at the factory he spent 2 days and night listening to the generator and scribbling on his notebook.

After that he asked for a ladder, climbed on it, put a chalk mark on a specific spot and explain to the engineers that they needed to remove the plate and replace sixteen windings behind the plate. After that the generator worked perfectly and Ford received a $10 000 bill.

Ford asked for an itemized bill and Steinmetz sent this

• Making chalk mark on generator $1.
• Knowing where to make mark $9,999.

Ford paid the bill.