cobbler, stick to your last

Do not advise about or interfere with matters of which you know little or nothing. This turn of phrase comes from an anecdote about a painter of ancient Greece named Apelles. One day a shoemaker saw a painting of his and pointed out that the shoe in the picture was not accurately portrayed. The painter corrected that part of the picture. Then the next day the shoemaker pointed out a mistake in the painting of a leg. But the painter replied, “Shoemaker, do not go above your last.” The story was repeated in various accounts and made its way into John Taverner’s translation of Erasmus as “Let not the shoemaker go beyonde his shoe.” Although the cobbler’s day appears to be nearly over, at least in America, the cliché survives.