Apron: the lower member under the sill of the interior casing of a window.
Blind Stop: A rectangular molding used in the assemblage of a window frame; nailed between the outside trim and the outside sashes, it serves as a stop for storm sashes and screens and assists in preventing air infiltration.
Drip Cap: a molding over an opening for catching and shedding rain water.
Double Glazing: Use of two panes of glass in a window to increase energy efficiency and provide other performance benefits. May or may not refer to an insulating glass unit.
Exterior Casing: Exposed moulding or profile around a window or door on the outside, to cover the space between the window frame or door jamb and the wall.
Head: Main horizontal frame member at the top of a window or door.
Inside Casing: Exposed moulding or profile around a window or door on the inside, to cover the space between the window frame or door jamb and the wall.
Jamb: Main vertical members forming the sides of a window or door frame.
Meeting Rails (Check Rail): The bottom rail on the upper sash and the upper rail of the lower sash of a double-hung window unit, where the lock is mounted. Also referred to as a meeting rail.
Muntin (Grille): Profile or moulding, either vertical or horizontal, used to separate glass in a sash into multiple lites. Generally refers to components used to construct divided lite grids or grilles simulating a divided lite look.
Sash: An assembly of stiles and rails (vertical and horizontal members) made into a frame for holding glass.
Sash Stop: A small strip nailed or screwed around a cased frame to hold a sash (of a double-hung window) in place; also called a window stop.
Sheathing: Sheets of plywood, gypsum board, or other material nailed to the outside face of studs as a base for exterior siding. This exterior wall covering adds structural strength and serves as a vapor barrier.
Siding: Cladding material for the outside of a building.
Parting Stop: A narrow strip, either integral or applied, that holds a sash or panel in position in a frame.
Sill: The main horizontal member forming the bottom of the frame of a window or door.
Sub Sill: A subsidiary sill member fitted to a window frame; serves as a stop for screens; causes water to drip farther away from the wall surface; also called a sill drip molding.
Stool: A horizontal board or plate at the windowsill on the inside of the window, fitted against the bottom rail of the lower sash to form a base for the casing.
Rail: Horizontal member of the framework of a window sash or door.