  Let $\mathcal{C}$ be a small category. We investigate ringed sites
$(\mathbf{C},\mathfrak{R})$ on $\mathcal{C}$ and the resulting module
categories $\mathfrak{M}{\rm od}\text{-}\mathfrak{R}$. When $\mathcal{C}$ is
finite, based on Grothendieck and Verdier's classification of finite topoi, we
prove that each $\mathfrak{M}{\rm od}\text{-}\mathfrak{R}$ is equivalent to
${\rm Mod}\text{-}\mathfrak{R}|_{\mathcal{D}}[\mathcal{D}]$, where
$\mathfrak{R}|_{\mathcal{D}}[\mathcal{D}]$ is the skew category algebra,
canonically defined on $(\mathbf{C},\mathfrak{R})$, for a uniquely determined
full subcategory $\mathcal{D}\subset\mathcal{C}$ and the restriction
$\mathfrak{R}|_{\mathcal{D}}$ of $\mathfrak{R}$ to $\mathcal{D}$.
