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Generally, there are only four different regimes: the standard alternating stabs (CH, BR, QO, HOM, Siemens), standard with space-straddling (GE and FPE), side-by-side busing (Pushmatic), or both-at-once busing (Zinsco). All the named panels except GE are obsolete.

Generally, there are only four different regimes: the standard alternating stabs (CH, BR, QO, HOM, Siemens), standard with space-straddling (GE and FPE), side-by-side busing (Pushmatic), or both-at-once busing (Zinsco). Pushmatic is obsolete, and FPE and Zinsco are dangerous.

By the way, in a modern North American/Philippine panel, prudent choice of circuit breaker and respecting keying will guarantee correct attachment to the prefab buses. On the other 5 continents, breakers are often "DIN Rail" mounted and hand-hardwired on both sides, meaning miswiring is possible.

How it's done by electricians is that they are familiar with the busing inside the service panel in question, and they know what they're punching down into. Also, anytime phase matters, they are using a multipole breaker (or at least handle-ties) which enforce phase choice for them, via keying.

Generally, there are only four different regimes: the standard alternating stabs (CH, BR, QO, HOM, Siemens), standard with space-straddling (GE and FPE), side-by-side busing (Pushmatic), or both-at-once busing (Zinsco). All the named panels except GE are obsolete.