3.14章，提及，Other socket-outlets shall be mounted in the minimum size intended enclosure or wall box.

Note: An appropriate metallic enclosure for socket-outlets on mounting plates of approximately H 114mm x W 72mm with 84mm certres is one of H 90 mm x W 60 mm x D 40mm(approximating dimensions of commonly available units).

怎么都看不懂这句话的语法，不清楚缩写 H，W，D到底是什么，不明白到底是个什么形状的东西，尺寸要求如何？

请哪位高手出手帮忙解答，万分感谢！