harshness, that's one part of the daunting understanding of surge protection I had. What structurally makes a main box a main box? Two buidlings I had wired by an electrician have what look to me like distribution breaker boxes as a main--multiple slots for circuits, one acting as a main switch. Besides acting as a main switch in the main line, I've only added one circuit breaker to a surge device. One building I asked to have a whole-home-outdoor surge protector installed at the same time as initial power hook up and what was professionally installed looks to me like a distribution box, multiple slots for circuits, one acting as a main switch. Another way I've seen it dones by a power utility is install a surge device wired to the meter--no switch required, as a Type 1 Surge Protection Device (SPD).