几百英尺外都能看到这些金属桶。
有一种叫做沟槽支撑的东西——一种用于挡住沟壁的金属箱体——挖土超过五英尺约1.5米时，用它来防止塌方。
There's something called a trench box - a metal case that holds back the sides of the walls - to be used to stop them caving in when you dig deeper than 5ft.
就在几周前，飞机工程师才发现他们并没有完全了解金属疲劳——四月一日，西北航空公司812航班使用的波音737-300型客机在从凤凰城飞往萨克拉门托的途中发现在机身的上半部有一个五英尺的裂纹，不得不紧急迫降。
Over the past few weeks, aircraft engineers have found they do not know quite as much about metal fatigue as they thought.
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