Boundaries

"Ive placed land mines around my bedroom door.  Thus, if the cleaner zooms is within 20 feet of my room it'll be a good joke on our maid.  The only disadvantage is that, after a direct hit, you have to get a new vacuum cleaner.  Also a new maid." --Groucho Marx

The joke reveals a truth: boundaries are to be seen and respected.  According to the Talmud a four foot invisible perimeter surrounds each person.  When we come within that area we are within their boundary.