我周五安装一个rocking chair，用到rachet,发现它在狭小的空间里非常好用，我感动的快哭了

美国机械设计和制造真的厉害。

 

In 1863, the American J.J. Richardson patented the first design for a ratcheting wrench with different-sized sockets that could be swapped out for each other. Originally, these wrenches had square-shaped sockets, as they were easier to make.