We first consider discrete nets in the standard Euclidean 3-space \(\mathbb {R}^3\) with the standard Euclidean metric. For simplicity, let our domain be \(\mathbb {Z}^2\) ; however, the theory will hold true for subdomains of \(\mathbb {Z}^2\) . An elementary quadrilateral is a quadrilateral composed of vertices \((m,n)\) , \((m+1,n)\) , \((m+1,n+1)\) , \((m,n+1)\) , for some \(m,n \in \mathbb {Z}\) , where we often denote the four points by i, j, k, \(\ell \) , respectively, so that they are ordered counterclockwise about the quadrilateral and starting with i at the lower left vertex.