Vertex-degree-based topological indices have been widely investigated and used in chemical graph theory for describing, predicting and explaining physical, chemical and biological properties of molecules. As opposed to the large body of research on these indices for planar and molecular graphs, little has been done on their computation for 3D crystallographic structures. We fill this gap by computing some of the most widely used vertex-degree-based topological indices of rectangular blocks of unit cells in one of the basic crystallographic structures, the simple cubic grid.