shoe / caligae stress analysis

[Neuraleanus]

I think I need to be sure what you mean by "ankle strap"

Referring to the second pattern from the top of my caligae page, the Mainz caliga, the "ankle straps" are labeled 2a and 2b. Perhaps "mid-strap" is a better label. The basic idea is to keep your heel from moving. If the heel rubs you get blisters. The most difficult part of making caligae is getting the pattern correct.