So, often on the front of the locomotive is a large iron wedge for clearing objects off the tracks.

通常在火车头前面有一个大铁楔用来清理铁轨上的东西。通常俗称" 排障器" （抓牛器）。

Into the crack he slipped the thin edge of an iron wedge.

他把铁楔子的薄边塞进裂缝里。

He drove blocks of wood into it, and moved the iron wedge higher.

他把木块塞进去，把铁楔子移得更高。