loader-unloader

例句：

1. 1.The loader is used to load the truck with materials.
   装载机用来给卡车装载材料。
2. 2.The unloader is used to unload the truck and remove the materials.
   卸载机用来卸载卡车并移除材料。
3. 3.The loader and unloader are essential tools for construction workers.
   装载机和卸载机是建筑工人必不可少的工具。