Dear Master Cecil: I have been educated by this Forum to understand the following: If the front door leads directlyto a hallway, there should not be a window or a door at the end of this hallwayin the back of the house. It isone of theprimary causes of"chi" leakage. Now, I have a wall at the end of this hallway in the back of the house. In order to let natural light comeinside the back end of the house, I plan to install glasses in that wall. As you know, the glasses are not windows. We can open windows; but, we cannot open glasses. Do those glasses also result in "chi" leakage? Do the glasses must be installed at a height above the top of the front door to prevent "chi" leakage? Thank you for your advices. Regards, Jen