Imagine that you open a door, then you place your two hands on the top corner (furthest from the hinges) and hang with your full weight. Did you ever do that as a kid? I know I did, and all my four boys certainly have as well! Initially, the door will be able to tolerate that stress but now imagine that you have the strength endurance of a rock climber and hang there whilst the door is swinging back and forth. In time, this stress and leverage on the hinges, will over demand