Greek sandals-soles

[Giannis K. Hoplite]

I remember reference to greek shoes having hobnails. But i haven't ever seen them in art,nor have seen actual hobnails in any museum. Has anybody reference to ancient greek hobnails? If nor,how else would they make the soles?
Any sources for accurate(even roman) hobnails?
I'm trying to use caligae construction in order to guide a manufacturer make me greek sandals.I'm mainly interested on how the back stitch was made. Was it reinforced? I have seen caligae both with reinforcement of a leather stipe and without, What is more accurate? In some photos of ancient surviving caligae that i have seen there doesn't seem tho have any reenforcement,but most reconstructions have. What is more accurate?
There were not greek military sandals so evidence from any kind of shoes would be of interest.
Thanks
Khairete
Giannis