knock yourself out: 尽自己最大的努力
Don't knock yourself out looking for them.
不必费牛劲找他们了。
Why don't you knock yourself out and help yourself to finger food?
为什么不歇会儿吃点东西?

appeal to: 请求
The company is prepared to trade off its up-market image against a stronger appeal to teenage buyers.
该公司拟改变只售高档商品的形像，以吸引青少年顾客。
This policy will not appeal to the voters.
这项政策不会受到选民的欢迎。