I see the term "Last" on boot manufacturer' sites, but have not been able to locate a definition. To what are they referring?
A "Last" is a substitute foot cavity used by the manufacturers. Some measure with liner aswell, this measurement is often misleading. We have during the super cold spell this winter "water filled" boots, frozen them and measured the width as suggested by the manufacturers of the frozen "last/plug". This also enabled us to measure instep height, heel width. Our measurement showed gross mis information regarding ceratin brands. Never the less, the guide itself (ie 98mm) is a good one if looking for certain charachteristics of boots.