Caligae Construction

[Neuraleanus]

Sorry, I was meaning the horizontal seam at the base of the heel- not the vertical one. I dont' doubt the latter was strong, but with the way caliga designs are, there isn't much or any leather to fold under the heel to securely connect the upper at that point (it seems to me). That's where I'd expect a fair amount of stress on the seam if the sandals are worn a lot, for extended periods, or in adverse weather conditions

After completely stitching up the back, I left the region between the upper and the soles open. Where is this "horizontal seam" in this pattern?