On a recent morning, Charles Courtney sat in his workshop at Universal Artificial Limb Co. in Silver Spring holding a plaster cast of someone's knee.

Courtney is a large man with a gravelly voice. But when he handles a cast, his movements are delicate. "This is why your feet feel tingly when they fall asleep," he said, tracing one side of the limb with his index finger. "There's a nerve that runs through here."

Putting the cast down, Courtney reaches for a clear plastic exoskeleton of the limb, one of the many intermediate molds created to fit a prosthesis. The transparent version of the limb, he said, allows him to see where the tibia presses against the side of the prosthesis's wall. It's so he knows whether he has to make an adjustment. "Otherwise, you'll get a blister, and it will open up and bleed," he said.

Courtney likens his work at Universal, the oldest continuously operating prosthetic and orthotics business in the Washington area, to "a dress fitting, but more intimate."

For Silver Spring residents, Universal's classic storefront, with its name painted in gold letters on the window, has been part of the landscape of downtown for nearly 40 years. In recent weeks, however, a "For Rent" placard has gone up in the front window, and a banner that reads "For Rent" hangs along the front of the one-story building on Wayne Avenue.

Courtney said his lease is up in five months, and his landlord intends to triple his rent. He said he is scouting for a new location among storefronts around Silver Spring.

The sight of the "For Rent" sign alarmed Silver Spring preservationists such as Jerry McCoy, president of the Silver Spring Historical Society, who laments the growing loss of longtime businesses such as Universal. "I guess old-time nostalgic businesses are not deemed sexy to the customers of the 21st century," McCoy said.

Courtney bought the company from the Caron family, who founded Universal Artificial Limb in 1919, shortly after World War I. The business was originally at 617 F St. NW in Washington, now the site of the MCI Center. The Carons relocated to downtown Silver Spring in 1965. Courtney, an employee, took over in 1978.

Having to move is just one of Courtney's recent challenges. Universal has survived industry consolidation, falling prices for its services from health care providers and rising costs caused by technological advances.

Courtney and his employees map the idiosyncrasies of the human body with tape measures and cast plaster molds in ovens in the back of the establishment. They produce custom-designed prostheses using an assortment of wooden vises, files and pliers that line the walls of the workshop.

Despite the antiquated feel of his space, Courtney embraces new technology. Universal holds 12 patents, including some for foot and hand prostheses. A decade ago, Universal was one of the first in the area to begin using a CAD-CAM, a computer-assisted design and computer-assisted manufacturing machine. The CAD-CAM can scan a mold, digitize its dimensions, store the information in a computer and later re-create the mold as a piece of foam.

Creating the original mold, however, still demands a hands-on approach. "There are pros and cons to what a computer can do," he said. "Everybody is different."

Being able to manufacture prostheses on-site allows Universal to make adjustments immediately, Courtney said. When Universal moves, he may downsize and move the manufacturing elsewhere, he said.

Keeping costs down has become more imperative now that Universal must compete not just with other independent operators, but with industry behemoth Hanger Orthopedic Group, which is based in Bethesda. Hanger owns and operates about 600 patient care centers and employs more than 3,000 people nationwide. Through its Southern Prosthetic Supply, it sells products to other companies. Hanger also owns the country's only orthotic and prosthetic managed care network.

Courtney said Hanger has made life harder for small operators such as himself. Because it is larger, Hanger can afford to advertise, which Courtney says he cannot do. Hanger is also in a better position to negotiate prices.

In addition, over the past decade the health insurance industry has pushed down prices for orthopedic and prosthetic services. Courtney said that as a result, he has had to downsize from 13 employees to four.

He said Universal has survived on referrals from hospitals and word of mouth. Universal's reputation has attracted customers from as far away as Brazil.

Courtney said he also donates his services to war victims, such as a young man from Bosnia who lost his hands to a grenade. Right after Courtney fitted him with a new hand, the young man picked up a pen, wrote his name and drew a picture, which Courtney keeps in a photo album. The album also contains pictures of especially challenging cases, such as the young man who lost both of his arms while installing a television antenna on his roof, or the boy who lost his left foot to a lawn mower.

He said he isn't worried that he will lose any customers when he moves. "It's like when someone tries to open up [a store] between you and your customer," he said. "[The customer] might stop in [the competition]. When they find they don't get the service or familiarity, they find you."

Universal Artificial Limb Co., which has operated in downtown Silver Spring since 1965, will need to find a new home.