What characteristics do the gang's two named exploits --pinching free rides and destroying the house-- have in common?
Greene uses both activities to show the lost nature of young people. It makes sense that the gang's initial meeting place s a cratered out parking lot. Their lives are in a "parking lot" of sorts. There is no real definition and no real purpose to their activities and their being. The gang seems to be waiting. They pinch rides, almost going nowhere fast and for free. T.'s desire to lead the gang in breaking down Mr. Thomas' house is another reflection of mindless destruction, something that seems good at the moment, but lacks any real transcendent meaning. Part of the reason that T. loses control of his leadership post is because he cannot provide any substantive purpose to what it is they do and why the gang does it.
Greene is able to evoke a certain level of sadness in the young people of his story. Whether it is pinching free rides or destroying the house, the young people in the story lack not only a moral fiber, but a purpose of being. Their lives are empty and vacuous, concerned with temporal and contingent vehicles of gratification. Yet, they lack any real structure or any real meaning. This becomes clear when Mr. Thomas is locked in the bathroom and the children run away. When confronted with real and hard implications of their actions, there is only flight evident. It is in this light where one can see that the characteristics of the gang's two main exploits are similar.