troll line

例句：

1. 1. The engineers are using a troll line to dig the tunnel.
   工程师们正在使用一条隧道线来挖隧道。
2. 2. The construction workers were working on a troll line for several hours.
   建筑工人在一条隧道线上工作了几个小时。
3. 3. The troll line was used to mark the boundaries of the new road.
   隧道线被用来标记新道路的边界。