a tape foot or last measurement around the arch, instep or cone, and waist
How far between the ball and heel this measurement is taken varies between makers. Some purposefully feel for the intermediate and lateral cuneiform bones and measure over them.
Video: Bill Bird following the groove between first and second metatarsals up to find the anterior “lip” of the second cuneiform bones or instep girth measurement
Instep girths can be important for ensuring intended spacing of facings for laced shoes. If a laced shoe is too wide around the arch, the facings may touch before the instep is held securely. If the shoe is too narrow around the arch, the facings may have to spread quite far apart in order to fit the foot.