When setting up model based on the discontinuous Galerkin time explicit interfaces it can be advantageous to use assemblies in the geometry and pair conditions in the physics interface. This allows to use non-conforming meshes at the interface between, for example, two materials. Different materials are used in the different parts of the assembly. To couple the parts, at the physics level, the pair boundary conditions should be used. They are in general available from the Pairs submenu.