During excavations at the Markul fortified settlement, Republic of Abkhazia, a cluster of iron items, including nails, was found. Nails usually draw little attention as they cannot serve as chronological indicators. Several attempts at constructing a typology of nails have proved unsuccessful. The quality of metal of which they were forged has not been studied purposefully, although it can be relevant to the use of nails and construction practices. Here, we present the results of a metallographic analysis of 19 nails from Markul (13 spec. from a simultaneously formed cluster of iron items, and six spec. found elsewhere at the site). The findings suggest that they can be subdivided into three types in terms of metal structure and, accordingly, of properties of nails: those with a ferrite structure (“soft”), those with a ferrite-pearlite structure (“strong”), and those with a cementite structure (“extra strong”). These types correlate with three types of construction materials used in Abkhazia in the Late Classic and Medieval period. Lack of correlation between metric properties of nails and metal structure suggests that the latter was intentionally formed for specific tasks, depending on the characteristics of the details joined by nails.