I always wondered why Jack chose the shirts, specifically, as the symbol for his love for Ennis. When I first saw the movie, I think it was probably the most touching and romantic thing I have ever seen a film. I don't think I ever would have thought of keeping two shirts, folded into each other like that, so I think it was so sweet on Jack's part, and lovely that he thought of that. I also believe that Jack's mother knew everything. I think Jack confided in her, he must have told her they have a special meaning, because she kept them just like they were. I think it was after that very first summer, when Jack goes and spends the fall/winter with his parents. He probably hung the shirts up in his room, and one day when his mother tried to wash them, he told her to keep them the way they are because they were not just any shirts, they had a very deep meaning behind them. It's at that time he would have told her about Ennis, and felt comfortable talking to his mother about that topic for the first time in his life. When Ennis comes to visit after all those years, she knows exactly who he is and what he meant to her son. This was the Ennis Del Mar, the one, the other half of Jack's soul, and the way she treated him with such respect and kindness tells that she knew that he was not just a buddy of Jack's, but the love of his life.