Tiě sī (铁丝) refers to a wire-like finished product made of drawn iron, which is divided into many types according to its thickness. From Xiao Hong's People Outside the Family: "The last time the brass lock of that box popped, I realized that what he was twisting was a piece of iron wire."

The hot metal billet is rolled into a 5mm thick steel bar, which is then put into the wire drawing device to be pulled into different diameter lines, and gradually reduce the aperture of the drawing disk, and then cooled, annealed, coated and plated to make a variety of different specifications of the wire. The specifications of iron wire for bookbinding are as follows according to the industry standard: 0.50mm diameter 25# iron wire, 0.55mm diameter 24# iron wire, 0.60mm diameter 23# iron wire and 0.70mm diameter 22# iron wire, and so on.