Door and window terms, in plain English.

Terms A to Z

Bi-fold door

Hinged panels that fold against each other and stack at one or both sides of the opening.

Espagnolette

The locking bar inside a tilt-and-turn sash that moves the locking points around the frame.

Flashing

Waterproof tape or metal lapped around an opening so water runs outward, never behind the frame.

Full-frame replacement

Removing the old window down to the rough opening, then flashing and installing a new unit.

Header

The structural beam over an opening that carries the load above. Wider openings need deeper or engineered headers.

Hydraulic closer

An oil-damped mechanism, often hidden in a pivot, that controls how fast a door closes and latches.

Insert replacement

Installing a new window inside the existing frame, keeping interior and exterior trim.

Insulated glass unit (IGU)

Two or three panes sealed together with a spacer and a gas or air gap between them.

King stud and jack stud

Full-height studs at each side of an opening (king) and the shorter studs that support the header (jack).

Lift-and-slide

A sliding door whose handle lifts the panel onto rollers to move and lowers it onto seals when closed.

Low-E coating

A thin metallic coating on the glass that reflects heat, lowering energy loss.

Multi-point lock

A lock that engages the frame at several points along the door edge at once, for security and a tighter seal.

Multi-slide

A door with several panels on separate tracks that stack at the side or slide into a wall pocket.

NFRC label

The National Fenestration Rating Council label listing a product's tested energy ratings.

Offset pivot

A pivot set a few inches in from the edge of the door, so it behaves much like a hinged door.

Pivot door

A door that rotates on pins at the floor and head instead of side hinges, allowing very large leaves.

Pocket

A cavity built into a wall that multi-slide panels slide into, clearing the whole opening.

Rough opening (RO)

The framed opening in the wall before the door or window goes in. It is slightly larger than the unit so there is room to shim and seal.

RRP rule

The EPA Renovation, Repair and Painting rule, requiring certified firms and lead-safe practices in pre-1978 homes.

Safety glazing

Tempered or laminated glass required in and near doors, near floors and in wet areas, marked with a permanent certification etch.

SHGC

Solar heat gain coefficient: how much solar heat comes through. Lower means less summer heat.

Shop drawings

The manufacturer's detailed drawings of a door or window with exact sizes and details, approved before production.

Sill pan

A sloped, waterproof tray under a door or window sill that catches any water that gets past the frame and drains it outside.

Thermal break

An insulating strip, often polyamide, between the inside and outside parts of an aluminum frame, to stop heat and cold passing through.

Threshold

The strip at the bottom of a door opening. A flush threshold sits level with the finished floor.

Tilt-and-turn window

An inward-opening window that tilts in at the top for ventilation or swings in like a door, from one handle.

Traffic door

On a bi-fold system, the one panel that opens like a normal door for daily use.

U-factor

How much heat passes through the whole window or door. Lower is better. Climate zone 4A code maximum is 0.30 under the 2021 IRC prescriptive path.

Unit dimension

The actual outside size of the door or window frame. Factories build to this, so it must be worked out from the rough opening, not confused with it.

Weep holes

Small drainage slots at the bottom of a frame or sill that let water out. They must stay clear.

Sources

1. IRC 2021 fenestration U-factor by climate zone (Jaspector summary)
2. Importing aluminum windows and doors from China: technical guide (HSY Sourcing)
3. US EPA: Renovation, Repair and Painting (RRP) Program for contractors

Written and reviewed by DDA Construction · Updated September 2026