"A turnshoe is a type of leather shoe that was used during the Middle Ages. It was so named because it was put together inside out, ...
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and then was turned right-side-out once finished: this hides the main seam between the sole and vamp—prolonging the life of the shoe and inhibiting moisture leaking in through the seam.
In the beginning, turnshoes consisted of only one piece of leather sewn on only one side. In the late early and the high medieval ages, turnshoes mostly consisted of one sole (cowhide or bovinae) and one piece of vamp or upper (goat or cowhide or caprinae/bovinae). In the late Middle Ages, additional elements were added, like doubled soles." - (en.wikipedia.org 24.10.2019)