Knowing where to tap

Knowing where to tap
>
> A giant ship engine failed. The ship's owners tried one expert after
> another, but none of them could figure but how to fix the engine.
>
> Then they brought in an old man who had been fixing ships since he was
> a young. He carried a large bag of tools with him, and when he
> arrived, he immediately went to work. He inspected the engine very
> carefully, top to bottom.
>
> Two of the ship's owners were there, watching this man, hoping he
> would know what to do. After looking things over, the old man reached
> into his bag and pulled out a small hammer. He gently tapped
> something. Instantly, the engine lurched into life. He carefully put
> his hammer away. The engine was fixed!
> A week later, the owners received a bill from the old man for ten
> thousand dollars.
>
> "What?!" the owners exclaimed. "He hardly did anything!"
> So they wrote the old man a note saying, "Please send us an itemized bill."
>
> The man sent a bill that read:
>
>
> Tapping with a hammer....... ........ ........ $ 2.00
> Knowing where to tap......... ........ ......... $ 9,998.00
>
>
> Moral of the story is . . . . . . . . .... .. .
>
>
> "Effort is important, but knowing where to make an effort makes all
> the difference"