A boss who runs a factory with a very large and complicated machine finds one morning that the machine is broken down and nobody knows what to do. He has to get it up and running again but like everyone else doesn't know how to fix the problem.

They call in a technician who comes in, takes a look at the machine, goes around the back of it and hits the machine with a hammer just once on a precise spot. The machine starts working again.

Next day, the boss gets the bill in the mail for $1000. He is furious as to how anyone can have the nerve to charge that much just for hitting something with a hammer. He gets his secretary to ring the technician up and ask for a detailed invoice.

The following day he receives the detailed invoice which reads:

Hitting the machine with a hammer ------------------ $1.00
Knowing where to hit the machine ------------------ $999.00