A man calls a refrigerator repair service. "My refrigerator isn't working."

"What kind is it?"

"It's a small one."

"Electric, gas or propane?"

"Propane."

"Ah! Then the problem is most likely vapor lock. You don't need a service call, just turn the refrigerator upside down for a few minutes to allow the lock to clear. Then put it back and all should be well."

Second call, a few minutes later. "The least you could have done is to tell me to empty the fridge first!"