The Complete Handbook of Mail Slots

Chapter 1: Understanding Mail Slots

A mail slot, at its simplest, is a cut-out in a door or wall with a hinged flap on the exterior and a framed opening on the interior. Its purpose is to permit the passage of letters and small flat packages without opening the door. But that simple description masks the true scope of what a mail slot must do: it must keep weather out, security intact, and fire and drafts at bay, while remaining functional for a delivery vehicle that is carrying a load in a hurry. The failure modes are many - water leaks, frozen flaps, air infiltration, corrosion - and they all stem from a device that is being asked to be a through-wall opening while simultaneously acting as a barrier. Understanding the actual demands placed on this device is the starting point for specification and installation.

In practice, a mail slot is used most often on a front door, but it is not inherently a door product. The term "mail slot" also applies to through-wall units used in apartment buildings, commercial storefronts, and service vestibules. In each case, the physical requirements differ. On a residential door, you are cutting into a single panel of wood, fiberglass, or steel that may be only 1.75 inches thick. In a masonry wall, you have a cavity left between blocks that is often 6 inches or more, requiring a longer sleeve for the slot. A slot for a commercial door with a hollow metal frame