flat threaded steel

例句：

1. 1. The floor is flat and easy to clean.
   地板是平坦的，容易清洁。
2. 2. The table is flat and can hold a lot of food.
   桌子是平坦的，可以放很多食物。
3. 3. The road is flat and easy to drive on.
   道路是平坦的，易于驾驶。