The Door With a Mezuzah

Rav Chaim's home was completely open to anyone who wished to enter. People ate his food, took away his seforim and even slept in his bed, leaving him nowhere to sleep some nights. His concern for others was so great that it never occurred to anyone that they were inconveniencing him, and perhaps they really were not. His house was the local gathering place for anyone who had nowhere else to go.

Someone once asked why Rav Chaim had a door on his house at all, if it served no purpose and always stood open. The answer was obvious. According to one opinion, a mezuzah may only be placed on a doorway that has a door, and so the door was there to make sure that the mezuzah was fully lechatchila. Why else would anyone have a door?