horse-shoe main

例句：

1. 1.The horseshoe main is the most important part of the fence.
   马蹄形的主干是围栏最重要的部分。
2. 2. The horse-shaped main was made from a single piece of metal.
   马蹄形的主干是由一整块金属制成的。
3. 3.The horseshoe main was used to secure the fence in place.
   马蹄形的主干用来固定围栏。