Explore the intricacies of lattice topological phases in this comprehensive lecture by Fiona Burnell from the University of Minnesota, Twin Cities. Delivered at IPAM's Graduate Summer School on the Mathematics of Topological Phases of Matter, the talk delves into the fundamental concepts of lattice Hamiltonians, vector spaces, and local rules. Gain insights into the construction of Hamiltonians, including vertex terms and matrix elements, while understanding the importance of Hermitian properties and gauge choices. Investigate the underlying fusion and crossing principles that govern these systems. This in-depth presentation offers a valuable resource for graduate students and researchers interested in the mathematical foundations of topological phases in condensed matter physics.