Harry found others who needed help from him, too. Jack, a tall, strong boy with an unfortunate stutter, showed them some of the karate he'd learned but was forbidden to use against anyone who didn't throw a punch first—how to fall without being hurt, how to kick and punch effectively, how to dodge and block the clumsy strikes of untrained fighters. Mark, tiny and slight, had a talent for finding and exploring the back alleys, maintenance corridors, crawlspaces, and even rooftops of the places he went; he taught them how to open things that were meant to be closed, how to walk, climb and crawl silently, how to spot entrances and exits and guess what was behind them, how to build and hold a map of a place in your head. Neither of them were really friends, but they both sought Harry out for the protection he could give them from Dudley's gang and the friendliness they could get nowhere else, and he was happy to learn and teach.