switch-blade knife

• 弹簧折刀

switch-blade knife的用法和样例：

例句

1. The knife mechanism is essential to any folder.
   刀具的机械装置对任何折刀都是必须的。
2. The policmen seized the folding knife that was used by the scoundrels.
   干警缴获了歹徒用来行凶的折刀。