"Floreat" picture hangars look similar to the standard hardware section
ones of bent metal and a nail. The floreats, however, are well made,
with a precise hole for the nail, which is very thin, very rigid
tempered steel. We've used them for a while mostly on wallboard and they
hold forever, are easily removed, and hardly make a hole. Any fine art
picture framer should be able to order them for you. I've seen them in
various art and photography catalogs, too.
Bill Sander
Wells Fargo Historical Services