Reference
Mail Slot and Building Hardware Glossary
This glossary covers general terms used across mail slot replacement, performance testing, and historic preservation. Entries are kept generic rather than tied to any one product, so definitions here apply industry wide, not just to BOTA hardware.
Air infiltration
The uncontrolled movement of outside air into a building through cracks, gaps, or openings in the building envelope, rather than through intentional ventilation. See what air infiltration means for mail slots specifically.
ASTM E283
A standardized laboratory test method, published by ASTM International, that measures the rate of air leakage through a building component, such as a window, door, or door hardware assembly, under a set pressure difference. See the ASTM E283 explainer for how this standard applies to mail slot hardware specifically.
Building envelope
The physical separation between the inside of a building and the outside environment, including walls, windows, doors, and any hardware installed within them. A building envelope's performance is often measured by how much air, water, or sound it allows to pass through unintentionally.
cfm/ft2 and L/s/m2
Units used to express the rate of air leakage through a building component. Cfm/ft2, cubic feet per minute per square foot, is the imperial unit, and L/s/m2, liters per second per square meter, is the metric equivalent. Lower numbers indicate less air movement.
CSI MasterFormat
The standard numbering system, published by the Construction Specifications Institute, that architects, contractors, and manufacturers use to organize building products by category. See how mail slot hardware is classified under this system.
Drill template
A physical guide that shows the mounting hole positions for a piece of hardware, allowing an installer to see how it will mount on a door before installation.
Exfiltration
The uncontrolled movement of indoor air to the outside of a building, the reverse of infiltration. Measured the same way, and often tested alongside infiltration in a single test. See the air infiltration explainer for how both directions are tested.
Fenestration
Any opening in a building envelope designed to let in light, air, or people, including windows, skylights, and glazed door assemblies. Mail slot hardware is generally classified separately from fenestration, since it is filed under door hardware rather than window and door assemblies.
Gravity flap
A simple hinged cover on a mail slot that relies on its own weight to swing closed, rather than a spring, magnet, or other closure mechanism. Common on older or basic mail slots.
Historic homes
Homes generally recognized as significant due to their age, architecture, or historical association, often subject to preservation guidelines that affect what changes can be made to original doors and hardware.
Historic preservation
The practice of protecting and maintaining buildings, structures, and districts of historical, architectural, or cultural significance, often guided by local, state, or federal preservation standards.
LEED
Leadership in Energy and Environmental Design, a green building certification program administered by the U.S. Green Building Council. See LEED v4.1 Residential Single Family, EQ Prerequisite: Compartmentalization, p. 57 for the requirement relevant to air sealing in attached single family construction.
Letter size
A standard mail slot size, sized for standard mail and small packages. See the sizing guide for exact dimensions.
Magazine size
A standard mail slot size, sized for larger mail and catalogs without folding. See the sizing guide for exact dimensions.
Mail slot
An opening cut into a door, or the hardware installed in that opening, that allows mail to be delivered through a closed door without opening it. Mail slot hardware typically includes a flap or cover on one or both sides of the door to close the opening between deliveries.
Maximum allowable infiltration rate
The highest rate of air leakage a building component is permitted to have and still pass a given test standard, such as ASTM E283. A measured rate below the maximum allowable is a passing result, and the further below that limit, the stronger the result.
Neodymium magnet
A strong permanent magnet made from an alloy of neodymium, iron, and boron, commonly used in hardware applications that require a secure closure without a mechanical latch.
Noise transmission
The passage of sound through a building component from one side to the other. Gaps and openings in a building envelope, including mail slots, can allow more noise transmission than a fully sealed surface.
Pascals (Pa)
The metric unit of pressure used in air leakage testing to describe the pressure difference applied across a building component during a test, such as ASTM E283.
Pressure differential
The difference in air pressure between two sides of a building component, used to simulate wind or similar conditions during air leakage testing.
Renovation
Updating or improving an existing structure, typically without significantly altering its original structure or historical character. Compare with restoration.
Restoration
Returning a structure or component to its original appearance or condition, often used in the context of historic homes where original materials or designs are preserved or replicated rather than replaced with modern alternatives.
Retrofit hardware
Hardware designed to be installed into an existing opening or structure, rather than requiring new construction or a new opening to be created.
Rough opening
The unfinished opening cut into a door, wall, or other structure before hardware is installed, generally sized to accommodate the finished hardware.
Submittal
Official paperwork submitted by a contractor or supplier to prove a product meets a required standard or specification before it is approved for use on a project.
Weather stripping
Material installed around a door, window, or other opening to seal gaps and reduce air infiltration and exfiltration.
WELL Air Infiltration Management
A feature within the WELL Building Standard v2, administered by the International WELL Building Institute, that addresses air sealing at a building's exterior for commercial projects, focused on envelope commissioning and testing such as blower door testing.