As pieces of evidence accumulate use, multiple colors of highlighting and different thicknesses of underlining often occur, sometimes making it difficult to determine which portion of the evidence was read. If debaters stop before finishing the underlined or highlighted portion of a card, it is considered good form to "mark" the card to show where one stopped reading. To otherwise misrepresent how much of a card was read—either by stopping early or by skipping underlined or highlighted sections—is known as "cross-reading" or "clipping" which is generally considered cheating. Although many judges overtly condemn the practice on their paradigms, it is hard to enforce, especially if judges permit debaters to be excessively unclear. Opponents will generally stand behind a debater whom they believe to be cross-reading or clipping, as if waiting to take a card (see below), and silently read along with them in an attempt to get their opponent to stop or the judge to notice.