In the days of wooden warships, when men mustered at Quarters in the morning to check for presence and condition, it was customary to arrange them in neat ranks for counting, using the tar-filled seams in the deck as a reference for straightness. When the petty officer or Bos'n stood at one end and checked out the alignment, any man not properly located would be ordered to "toe the line." For midshipmen and boys, young fellows in training to be officers or sailors, standing for long periods toeing the line was a punishment for minor misdeeds. Today, of course, the phrase means that one should obey social rules.