lower frame rail

例句：

1. 1. The lower framerails of the car are designed tosupport the roof and protect passengers from theelements.
   汽车的下框架梁设计用来支撑车顶并保护乘客免受恶劣天气的影响。
2. 2. The engineer carefully inspected the lowerframe rails for any signs of wearor damage.
   工程师仔细检查了下框架梁，以寻找任何磨损或损坏的迹象。
3. 3.During construction, workers must ensure that thelower frame rails are securely fastenedto prevent accidents.
   在施工过程中，工人必须确保下框架梁被牢固地固定，以防止事故的发生。