WHAT TO LOOK FOR
• Working parts: Vintage doorknobs are beautiful but difficult to fit today’s modern precut doors. If you opt to use them as doorknobs, they need to be in good working order. Be aware that the mechanisms have changed so much over time that using them as functioning doorknobs can be challenging. “It’s like putting a Chevy engine in a Rolls Royce,” Jon Douglas says, noting that it is important to find a skilled craftsman to install the doorknobs.
• Door and hardware sets: Look for old doors with hardware included that have doorknobs in good working order. Make sure the knob has the small setscrew, or mount screw, in place because replacements are hard to find.
• Rare finds: Some styles of vintage knobs dating from the 1850s to the early 1900s, such as Sun Purple, that are in good condition are harder to track down and thus more valuable. Other rare collectibles include figural motifs that depict the heads of animals and women, and pieces crafted during the Art Deco period.

WHAT TO AVOID
• Reproductions: If authentic vintage is what you want, be cautious when buying doorknobs marketed as such. A newly manufactured knob sometimes is described as “vintage in style.” So read carefully and ask questions about age. If pieces truly are vintage and sold as a set, make sure that both knobs match before you buy.
• Lead paint: Vintage doorknobs that are painted may contain lead. If you find an old knob that is painted, ask the dealer about the paint. If he cannot tell you what kind of paint was used, either avoid the knob altogether or have the paint removed by a qualified technician.

WHERE TO FIND IT
• Internet and collectors: Join Antique Doorknob Collectors of America, and attend the organization’s annual convention; or go to its Web site, antiquedoorknobs.org. Check out eBay, which has a list of knobs in its antiques collection.
• Retailers: Look for vintage doorknobs at home-and-garden shops specializing in antiques, such as Figs and Relics, both in Phoenix. Or try antiques shops, including Brass Armadillo Antique Mall, Sage, or Stuff Antiques in Phoenix; and Granny G’s Shady Nook or Strunk’s Hollow, both in Glendale, Arizona.