http://www.ebookcafe-kyoto.com/word/chi.html
小口・のど・天・地・背など本の各部分の名称
http://blog.ddc.co.jp/mt/words/archives/20050810220823.html
I found them on the bottom of a box in a New Jersey antique shop filled with photographic junk from years gone by.
Shooting and Developing a 70+ Year Old Roll of Kodak Plus-X