Two paddies were working for the city public works department. One would
dig a hole and the other would follow behind him and fill the hole in.
 
They worked up one side of the street, then down the other, then moved
on to the next street, working furiously all day without rest, one man
digging a hole, the other filling it in again.
 
An onlooker was amazed at their hard work, but couldn't understand what
they were doing. So he asked the hole digger, " I'm impressed by the
effort you two are putting into your work, but I don't get it: why do
you dig a hole, only to have your partner follow behind and fill it up
again? "
 
The hole digger wiped his brow and sighed, " Well, I suppose it probably
looks odd because we're normally a three-person team. But today the lad
who plants the trees called in sick. "