sill beam

例句：

1. 1. The pillars of the building are made of stone.
   这座建筑的柱子是用石头做的。
2. 2. The beams of the roof are too weak to support the weight.
   屋顶的梁太弱了，承受不了重量。
3. 3. The beams of the bridge were so old that they had to be replaced.
   桥上的梁太旧了，不得不更换。