knock head against

Having suffered a head injury on United's summer tour of the United States and a knock to his shin against Chelsea last week, Hernandez is now back on the treatment table with a dead leg.

小豌豆已经是接连受伤，不仅在曼联的美国夏季巡回赛中头部受创，还在上周对阵切尔西时筋骨受伤，如今又带着腿伤重返伤兵名单。

By eight, I was so frustrated and desperate to sleep that I hit my head against the wall in the middle of the night; if I couldn't fall asleep, I thought, I'd knock myself out.

八岁的时候，我因为不能入眠而绝望至极，在半夜里用头去撞墙，心想如果再睡不着，就把自己撞死算了。

Please do not hold your head high, or you might knock your head against some protruding stalactite.

请别高昂着头，否则你的头可能撞到突出的钟乳石上。