A guy is sitting on a bench in the park eating his sandwiches. Looks over at two workmen with shovels and wheelbarrow, one digs a hole then the other one comes along and fills the hole back in. Slightly bemused, the guy on the bench finishes his lunch and gets ready to go back to work. As he's walking past the workmen he says 'er, I couldn't help but notice that you've been digging lots of holes and then filling them back in again, I just wondered why' to which one of the workmen replies 'the guy who plants the trees is off sick today'.