The arrangement of letters corresponds roughly to letter frequency, with the most frequently used letters on the left. The first two columns of keys are: e, t, a, o, i, n; and s, h, r, d, l, u. A Linotype operator would often deal with a typing error by running the fingers down these two rows, thus filling out the line with the nonsense words etaoin shrdlu. This is known as a "run down". It is often quicker to cast a bad slug than to hand-correct the line within the assembler. The slug with the run down is removed once it has been cast, or by the proofreader.