NEW YORK CITY - Elegant triple-tier Circassian walnut bookcases built into the 1906 Pierpont Morgan library in New York City are an inspiration in design, says architect Annabelle Selldorf.

She tells the New York Times the bookcases seem to float, since there are no visible stairs. These are hidden, and because of space constraints, rather narrow. Selldorf says she often designs in rolling ladders in such cases, not hidden stairs.

"We do a ot of custom library ladders in our projects, mostly from Putnam Rolling Ladder Co.," she says, calling them "one of the all-time great New York companies."

Samuel Putnam began making trestle ladders, step stools, pulpit ladders, industrial steel ladders and the famous "Classic No. 1" - the rolling library ladder, at the beginning of the 20th century. "The design hasn't changed since 1905," says Putnam president, Gregg Monsees.

Putnam residential rolling ladders were mostly placed by high-end architectural firms for wood-paneled home libraries of wealthy clients. From the 1920s through the 1970s, Putnam says its biggest customers were telephone companies, dry-goods stores, and clothiers like Brooks Brothers.

The building and renovation boom that started in the 1970s helped the firm survive as commercial clients dried up. Before 1980, Putnam made its ladders only from red oak. Now it also offers cherry, ash, hickory, beech, walnut, birch, maple, teak, and mahogany.

Putnam Rolling Ladders also supplies custom ladders to Rockler, which recommends them for wine cellars, home libraries, lofts, stock rooms, kitchens, and closets. "It endures the rigors of industry yet has the grace and beauty of fine furniture," says Rockler's site.

The standard ladder is made of the best grade red oak, which is filled and varnished. Each 4-1/2'' deep ladder step is dadoed and screwed to the 13/16'' thick rails, with strengthening rods under each step.

The ladder is measured vertically to a track up to 8' 11'' from the floor. Ladders can be made from other species and various lengths, delivered finished or unfinished.