Perhaps the ultimate glory of wood is that it can be shaped to almost any whim. And moldings -- which are those funny-shaped strips of wood with funny names like shoe, rail, ogee, crown -- are the obvious example of how well-shaped wood can shape a home.

A kind of wooden applique, molding has been used like embroidery on walls and ceilings for centuries. In addition to giving rooms a certain dignity, deep crown molding, for example, can be set away from the juncture of wall and ceiling to obscure lighting fixtures. It can also be mitered and shaped to form deep decorative cornices from which curtains are hung.

A multitude of sins can be hidden -- and often are -- behind molding. It is a truly artful disguise. These pre-cut decorative trims can create the effect of a right angle where a less-than-accurate carpenter has failed.

Moldings join a window to a wall and a wall to a floor. They outline doors, separate ceilings from floors, soften edges and make curves of corners. As ordinary as they seem in many houses, they can transform a commonplace room into an extraordinary space.

When Leo Patrick Cullinane puts up one of his high-priced Potomac houses, it's not only the proportions and the English Georgian styling that get noticed, but also the extravagant use of moldings. Recently, Cullinane built two sumptuous homes on five-acre plots. Each house has about $200,000 worth of wood moldings in it -- and it shows (thank goodness).

"I tried to combine the best of English Georgian architecture with some of the ideas Thomas Jefferson had," says Cullinane. In one of the $2-million houses, three molding-trimmed arches divide the living room from a step-down hall that leads to an outside terrace.

Arched windows, just beyond the living room arches, are framed with the same molding, but it is stepped a few inches away from the window to allow for special curtains or window treatments. This dramatic, graceful progression of space is defined by moldings.

In the same house, Cullinane ingeniously combined ornate crown molding -- the molding that is placed at the juncture of the ceiling and wall -- with a frieze. The frieze was cast from one at Jefferson's Monticello and was used in an exhibition at the National Gallery several years ago. The artisan who made and installed these ornate moldings, Dave Hytla, used the same friezes in the master bedroom of one house and in the two-story entry of the other house.

But moldings aren't always used to make a home ornate. A counterpoint to Cullinane's extravaganza is a small Cape Cod house owned by Mary Evans in Northwest Washington. With the help of architects Mark McInturff and John Wiebenson, Evans altered the first floor and opened it up. But that brought new problems: Spaces had to be defined and given unity.

Molding came to the rescue. The architects used one of the simplest, least expensive types made -- a 5/8-inch half-round, the sort usually used in concert with ogees, chair rails and crown moldings. They divided space by running the moldings in parallel bands around the room, up the stairs, connecting shelves together with walls and defining window frames.

The wall between the living and dining room was opened with rectangular cutouts. The shelves within these cutouts were set apart at the same two-foot intervals as the bands of molding. Thus the molding became edging for the shelves and at the same time worked to give the appearance that the shelf continued through the entire wall.

This treatment expands the view, carries the eye around the room, and emphasizes not the smallness of the space, but its expansiveness. Each band of molding is painted with semi-gloss white, and the bands of wall in-between are painted in gradually changing shades, from white -- at the very top -- to a pale green-gray at the bottom.

"I'm thrilled with it," Evans says. "It's such a simple, almost Japanese look, I had to get rid of all my heavy dark rosewood furniture just so you could appreciate the lightness it brings to the house."