knock on wood

knock on wood 在美国意为霉运去，好运来，有一种说法就是当遇上好运时立刻手触木头并说此话，以防厄运并期待好运持续，上天保佑，英式口语也会说成 touch wood.

I've never broken a bone, knock on wood.

我从未经历过骨折，上天保佑。

Cross your fingers, knock on wood: it's possible, though by no means certain, that the worst of the financial crisis is over.

叉上手指，敲敲木头，祈祷一下：如果可能的话（尽管我们无法确定），让这次金融危机最难过的部分就此结束吧。

knock/throw sb for a loop