Where Do Mezuzahs Go?

A mezuzah must be attached on the upper third of the right-hand side of the doorway as one enters, no less than one hand-breadth from the top.

Does a walk in closet need a mezuzah?

The mezuzah should be attached to the left side when walking from the room into the closet. If the floor area of the walk-in closet is so small that one does not actually walk into it when retrieving objects from the closet, then the doorway of the closet does not require a mezuzah.

What's a mezuzah used for?

The parchment that it is written on must be on the skin of a kosher animal. The purpose of the mezuzah is to act as a constant reminder of God's presence. Jews will often touch the mezuzah as they go through the door. The instruction for this comes from the Torah.