In one embodiment, a network device may have its network interfaces identified as either network-to-network interfaces configured to communicate with other network devices in a first computer network, or user-to-network interfaces configured to provide service to the first computer network for user devices. A fire hydrant has a keyhole in its sidewall. The image is scanned relative to the substrate surface so that each point in the process region receives a pulse of radiation sufficient to thermally process the region. Also, the interface layer may include a separation layer of a material different than the passivating material.