sport one's oak

One day that he had been writing a letter in Mr. Smalls' rooms, which were on the ground-floor, Verdant congratulated himself that his own rooms were on the third floor, and were thus removed from the possibility of his friends, when he had sported his oak, being able to get through his window to "chaff" him; but he soon discovered that rooms upstairs had also objectionable points in their private character, and were not altogether such eligible apartments as he had at first anticipated.