Sewing on cords gives the spine more support. This text block doesn't strictly need it - I could use tapes instead - but the cords create raised bands on the spine that show through the leather, as seen on medieval books. The sewing frame used in the video is from affordablebindingequipment.com

Using an awl to punch sewing stations; the punching cradle and guide ensure the measurements are consistent. You can also use a saw to create the holes; recessed cords require a wedge shaped to be sawn into the spine at every station for the cords to sit in.