coupler knuckle thrower

例句：

1. 1. The engineer used a coupler to connect the pipes together.
   工程师使用一个连接器将管道连接起来。
2. 2.The scientist discovered a new coupler that could be used for both electrical and mechanical connections.
   科学家发现了一种新的连接器，既可以用于电气连接，也可以用于机械连接。
3. 3.The construction workers used a coupler to tighten the bolts on the roof.
   建筑工人使用连接器来紧固屋顶上的螺栓。