Answer: Singer Sewn!
In Singer sewing, a small number of pages are sewn together through the spine with thread, usually using a converted Singer sewing machine. That’s right, many binders use converted Singers as well as industrial sewing machines made especially for binding books.
In either case, the basic stitch is the same – a basting stitch that resembles a line of en dashes on the outside with a simple interlocking loop on the inside.
A Machine with Needle and Thread
The process is straightforward and can be done in 2 ways: thread passing through the fold of the spine, or stitching next to the spine from top to bottom of the book block.
When the sewing is done through the fold, 4-page forms (a form is the properly imposed and printed sheet of paper before folding) are nested together to create a properly paginated book, sewn through the middle (the spine), folded along the spine, and then trimmed.
A signature (a form that has been folded to create reader pagination) could also be Singer sewn, but it would need to be opened – so it could lay flat like a piece of cloth – before going through the machine.
If your preference is to see the thread on the top and bottom of the covers rather than in the spine, the bindery can do a side stitch – Singer sewing along the side of the spine.