lay a hand on，lay one's hand on和lay hands on用法各不相同：
1. lay a hand on表示“动手打人”，只用于否定句和条件句中。
I bet he daren't lay a hand on her. 我打赌，他不敢打她。
If you lay a hand on his child，he will summon you for assault.
你要是碰一碰他的孩子，他会告你打人。
If you lay a hand on the child you'll be sorry.
如果你伤害这个孩子的话，你会后晦的。
2.lay one's hand on表示“得到，找到”，意同put/get one's hand on。
During those years I read everything I could lay my hands on.
那些年里，我能找到什么书就读什么书。
Patty began reading everything she could get her hands on.
帕蒂开始阅读她能找到的所有东西。
If he wanted to splash out on a new car it would take him a couple of days to get his hands on the cash
如果他想出一大笔钱买辆新车，他得花好几天才能筹到现款。
She devoured everything she could lay her hands on: books, magazines and newspapers.《牛津高阶英汉双解词典》
无论是书、杂志，还是报纸，只要能弄得到，她都看得津津有味。
devour dɪˈvaʊər/
vt.吞食；吞噬；吞没；毁灭；如饥似渴地读；(尤指因饥饿而)狼吞虎咽地吃光；津津有味地看
I know I have the stamp somewhere，but I cannot lay my hands on it at the moment. 我知道我有那枚邮票，可此刻却找不到了。
Wait till I get my hands on him!
等我抓住他再说！
He keeps everything he can lay his hands on.他占有每一样能得到手的东西。
I'll kill that son of a bitch when I get my hands on him!
我要是逮住那个王八蛋，非要了他的狗命不可！
3.lay hands on表示“捉住，逮住，对……动武”。
If I lay hands on that guy，I shall give him a good beating.
要是我抓住那个家伙，我要把他揍一顿。
If you lay hands on me like that again, I'll kill you.
你要是再那么伤害我,我就杀了你。
How dare you lay hands on me？你竟敢对我动武？
