看到一篇关于庭院装修文章中有一句话：
These are rope-wrapped posts，they look like decorativeelements in this space, but they're also 4 by 4 that securely hold up the网站优化verhead shades.
上面内容是描述用4根石柱撑起的遮阳棚，石柱用绳子缠绕包裹。
想请教这里用的短语4 by 4，我看四驱汽车也有写4 by 4的，所以这里4 by 4可否理解成4个一组、4个为一个单位的意思呢？
假如如此理解，短语4 by 4就是方法状语，可是方是状语在句中不可以放在表语地方，所以我感觉句子应该写成 but they alsosecurely hold up these overhead shades 4 by 4。
请老师指点我上面理解。
注意 4 by 4 后的that从句是定语从句，that 指代 4 by 4，且 that 从句谓语动词为复数形式。这足以对你说 4 by 4 在这里是用作名词的，而且是复数。所以你不可以觉得 4 by 4 是方法状语。WR 网站有一个 2 by 4 的问题，与你的句子中的状况类似。你可参读一个老外的解答。即 4 by 4 或 4 by 4 这种表达方法是美国建筑行业描述该截面积的一根木材。你的句子中的 post 并非石柱，应该是木柱，方形的，截面积为4英寸x 4 英寸。
The numbers are the dimensions in inches of acommon size of wood/lumber used in construction in the US. A "2 by 4"is a piece of wood of any length that came from such a piece . The lengths areusually numbers of feet a "ten foot 2x4", for example.
