crossbar automatic exchange system

例句：

1. 1. The carpenter used a crossbar to supportthe roof.
   木匠用一根横杆支撑屋顶。
2. 2. The bridge had a crossbar thatspanned the river.
   这座桥有一个横跨河流的横杆。
3. 3. The engineer used acrossbar to reinforce the beams.
   工程师用一根横杆加固梁。