What can a piece of string do? What can a piece of string do when tied to a piece of wood for a handle? It can start a less-than-perfect lawnmower to cut a less-than-perfect yard by two fellas who are trying hard to make honest money by doing honest work.
And when that one string breaks, leaving one strip of grass uncut, you learn how frustrating a piece of string can be; that same piece of string that held the whole thing together can turn its back on you and make the whole thing fall apart.
Then it finds grace in the amount of $40 that says, "All is well; God honors hard work," and sends them on their way.