3·I knocked my head against the doorpost and hurt it.
我的头撞在门柱上,碰破了。
4·I've banged into the doorpost and hurt my arm.
我撞着了门柱,把臂伤了。
5·The gatehouse, made by fine alloy plating casting, wood and plastics, consists of roof, door and doorpost with elegant features, embodies chinese traditional architectural art.