Cotton, muslin, gauze, crash, paper and other materials used to reinforce spines of library bound books. It provides the means for a firm connection between text block and cover and gives shape and firmness to the binding. Lock Stitch Lock stitches are the type made by household sewing machines, although the machines used by library binders are often larger. Mill The spines of books can be cut away on a milling machine to prepare them for double-fan adhesive binding or oversewing. After milling, a text block is comprised of loose leaves.
Notches are parallel grooves cut into the spine perpendicular to the binding edge.
The depth of the grooves and the distance between them can be adjusted to suit the size and weight of the text block. The covering material that extends beyond the edges of the boards and inlay before turning-in. The overhang becomes the turn-in. Rounding usually precedes backing. Rounding and backing help distribute the swell that naturally occurs with sewing and adhesive binding.