The moral meaning of Zunar is service. A soldier, a policeman, a postman, or a gatekeeper, when on duty, has a belt on, which expresses that he is on duty -- not free to do everything he wishes, but only that which he is appointed to his post to accomplish. This explains that man, as the most intelligent of God's creatures, is not supposed to lead his life as he wishes to lead it, but to consider the duty for which he is born and the service that he must render to God and His creatures. As man is apt to forget all that is not to his immediate interest, the loosing and the tying of the thread reminds him of his duty, as the belt reminds the soldier that he is on service. The idea is that we are all servants of God, and we must do all things for Him, Who has created us, supports us, and has engaged us in His service.