钉床

       原理：P=F/S

       根据压强公式，将人体重量分散到各个钉子上，每个钉子承受的压力只有十几克，钉子上升速度慢，是不会刺入人体的。

NAIL BED

      Principle: P=F/S

      According to the intensity of pressure formula, the weight of a person is distributed to every nail, the pressure of Each nail borne is only about 10 g and the rising speed is slow, so the nail can't stab into the human body.