Mezuzahs are posted on the right door post at the entrance to a room, on the lower part of the upper third of the doorpost. The mezuzah case is a cover to protect the parchment on which the first paragraph of the Shema is written. The Torah commands all Jews to hang a kosher mezuzah, written by a qualified scribe on parchment, on the doorpost of their front doors as well as doors inside the house. Artists throughout the ages have designed and produced cases to both protect the parchment from damage as well as beautify the mitzvah (commandment). Many cases have the Hebrew letter "Shin" appear on the case. The mezuzah case can be made of any material - some are transparent so that the parchment can be seen.