  A binary interface defect is any interface between two (not necessarily
invertible) domain walls. We compute all possible binary interface defects in
Kitaev's $\mathbb{Z}/p\mathbb{Z}$ model and all possible fusions between them.
Our methods can be applied to any Levin-Wen model. We also give physical
interpretations for each of the defects in the $\mathbb{Z}/p\mathbb{Z}$ model.
These physical interpretations provide a new graphical calculus which can be
used to compute defect fusion.
