My mezuzahs mean more than just the glass itself. I feel the objects with which we surround ourselves must have multiple layers of life. During WWll, my grandmother lived in Boston, but many of her relatives were in the Holocaust. Her meditation to stay focused was to make lace or tatting. I have replicated her lace patterns into my designs, and many of my mezuzahs have clear windows to read the Sh'mah inside. I choose to leave both top and bottom open so the spirit of "blessing" is easily spread within the home. Tiny put.....the blessing is not kosher. My mezuzahs are affixed with two sides of industrial grade Velcro so as not to harm your door frame.