A farmer challenges a physicist, engineer and plumber  to fence off the largest area of land using the least amount of fence.

The engineer declared that making the fence in a circle would be the most efficient.

The physicist said that a fence that followed the equator around the world would fence off the greatest area (half the earth).

The plumber laughed at the others, and with his design, won the contest.  What did he do?

The plumber simply made a small fence around himself and said he was on the outside. 

Sometimes you just gotta think outside the box, er, fence!