@Little Giant posted:jbmccormick: when you look at a modern wall outlet, the vertical slot on right is "incoming" 110 volts called "hot". The vertical slot on left (a bit longer) is the "outgoing" or neutral. Round hole middle lower is ground. On a 2 prong plug, the wider prong only fits the neutral slot. it is therefore "polarized". Older electric plugs are not polarized, its why older transformers need to be phased so their commons are the same. hope this helps.
A small phRasing issue: ALL.need to be phased if you use two or more together. The fat blade SHOULD help in elimination of the need but honestly, it has to be done to be safe. You can even find modern bricks where this is wrong internally in some batches. If anything it has to filed off or cord solder ends swapped at times. It is all about neutral vs hot safety to earth ground. Watch that hot one more so 
