The Amatis Border Router (AMBR) communicates wirelessly with the mesh network. The wireless signal can go through barrier types (drywall, cinderblock, etc.) but the signal strength will be reduced.
Recommendations:
mount your AMBR as central to the mesh network as possible for the most ideal interaction range
DO NOT place AMBR in a metal IT cabinet, or behind metal barriers which could block the signal from the AMBR to the mesh network
mount the AMBR close to the mesh and with the fewest barriers between the mesh