Thread Section Sewing or Sewn Binding is where a book is printed, collated, divided up into printed sections and then pages in a section are sewn together with thread. The individual sections are then either sewn into each other or bound enmasse into a bigger spine binding. This is probably the strongest and most thorough binding method, pages cannot be loosened or pulled apart easily and offers far greater long-term strength than most modern gluing methods.
Threading or sewing documents is one of the oldest and most failsafe binding methods, going back to the first days of print. When Shakespeare’s plays were first issued in quarto versions in 1594 these were sewn booklets that would be collected by persons and bound into larger volumes or collections. Many of the oldest printed books in existence have been held together by carefully sewn bindings that have stayed intact over hundreds of years!