Know your window replacement parts

Home improvement projects can sometimes be daunting for the average homeowner. Window replacement is no exception, and a short glossary and description of the parts of a window -- where each is located and what they all do -- can be helpful when purchasing new windows or repairing old ones.

What are window jambs?

On a double-hung window frame the vertical jambs (1) of the window house the tracks in which the window sash -- the parts that hold the glass -- slide up and down. These tracks are often simple wooden channels separated by a square section of wood -- the parting stop, so-called because it separates the tracks into two parts. An exterior stop and an interior stop complete the channels. In some windows, a vinyl jamb liner is included. The liner compresses to allow the sash to tilt out.

The horizontal head jamb (2) at the top, identical in form to the vertical jambs, and the sill (3) at the bottom, complete the frame. The sill is a thicker section of wood and is sloped to allow water to drain from the window.

Parts of the window sash

The vertical sections of the sash are stiles (4) and the horizontal sections are known as the top and bottom rails (5). The rails that meet in the middle are called meeting rails (6). Also called check rails, they are designed with opposing ledges to create a baffle that checks the flow of air.

Lites (7) are the glass (glazing) part of the window. They are held in the sash with waterproof adhesive -- a glazing material such as silicone or butyl -- and glazing beads (sometimes called glass stops). The beads finish the edge of the stiles and rails with wood right up to the very edge of the glass.

Between the panes, or on the exterior of the glass, decorative muntins (8), also called grilles, provide the effect of divided lites. "True muntins" separate individual lites of glass.

Indoor window parts

Vinyl windows, or any windows not as deep as the wall opening, may need wood extension jambs to extend or increase the depth of the jambs so the window frame reaches all the way to the drywall. A trim package adds finishing touches -- mitered moldings that surround the window; a stool (9), often mistakenly called a sill, which is typically 2 to 6 inches deep; and the apron, the piece of molding under the stool (10).

Most of the names for these double-hung window parts are the same for other styles of windows; however, casements, sliders, patio doors, and others may also have parts particular to those types of windows. Learning these names can make understanding your window salesperson or installer a lot easier when it's time for replacement windows.