哈哈,nominal vs acutal。
最常见的 2x4 的真实尺寸都是 1.5x3.5
Nominal Versus Actual: A History of the 2×4
Size standards, maximum moisture content, and nomenclature were agreed upon only as recently as 1964. The nominal 2×4 thus became the actual 1½ x 3½, imperceptibly, a fraction of an inch at a time. It was a 34 percent reduction in actual volume; as those in the trade would say, it’s “selling air.”