"I do wish, Holmes, you'd come over and dress down some of my non-coms.

I've been trying for three days to put 'pep' into some of them, and the K.O.

frowned at me this morning." "Non-com" is the Army abbreviation for "non-commissioned officers"-- -corporals and sergeants---while "K.O." is Army slang for commanding officer.
Arrived at an unpainted wooden barracks, in size and appearance just like those of the enlisted men, the three captains entered and walked up a flight of stairs to the floor above.

Here they passed through a narrow corridor with doors on both sides that bore the cards of the officers who slept behind the respective doors.

Cartwright went to his own room, while Greg followed Dick into the latter's quarters.
Plain enough was the room, seven and a half feet wide and ten feet in length, with a single sliding window at the front.