flat hole

例句：

1. 1.The flat hole in the wall is where the pipes run through.
   墙上的平洞是管道穿过的地方。
2. 2. The flat hole in the ground was filled with water after the storm.
   暴风雨过后，地面上的平洞被水填满了。
3. 3. The engineer carefully marked the flat hole on the map before starting the excavation.
   工程师在开始挖掘前，仔细在地图上标记了平洞的位置。