When was the only time Saul sees the Iron Sister? What does Father Leboutelier say about it?

Saul and Father Leboutelier were stashing hockey gear in the school basement. Saul saw the Iron Sister there. Father Leboutelier tells Saul to get away from it. He won't let Saul have anything to do with it. Saul asks why it exists and Father Leboutelier replies, "they lack charity".