An ordinary household electrical plug in the United States. Characterized by having two flat blades and a semi-round ground pin. There are several different variations on this theme: A plug rated at 20 amps will generally have one blade perpindicular to the other. A standard 15 amp plug has the two blades in parallel with each other. Modern versions are also polarized so the neutral blade is larger than the hot. That way even when there is no ground pin present the plug cannot be inserted backwards (which can, but usually doesn’t cause problems).