Touch wood - British English
Knock on wood - American English
This expression is said in order to avoid bad luck, either when you mention good luck that you have had in the past or when you mention hopes you have for the future. The expression is usually used in the hope that a good thing will continue to occur after it has been acknowledged.
"I have never broken my leg, touch wood." - I have never broken one of my legs and I hope that, with good luck, I never will.
"I was sick all of last week, but I think that I'm over it now, touch wood." - I'm hoping that I will continue to be better after being sick.
Touch wood is an example of a superstition: something that we do in order to have good luck. It is not based on human reason or scientific knowledge, but is connected with old ideas about magic and the supernatural.
It is commonly thought that touching wood has been a superstitious action to prevent evil throughout history.
Many languages and cultures have a similar superstition. Do you 'touch wood' in your country? What do you do to keep your good luck?
Link: What's happening - listening practice
Comments
superstition
have you ever trusted in supernatural? there a lot situation that people escape from dangerous ,you know , yesterday my brother shooted straight an arrow to me , but don't hit , touch wood
these 'have had' ,'has had'
these 'have had' ,'has had','had had' concept is not clear to me. I tried a lot to find out --how to use it?or where to use it?and its meaning or expression.but I failed.can u help me?
We touch wood too with the same thought in Turkey and
We sctrach our back(fanny) :\
when someone is looking us with an evil-eye. 
Thanks for the lesson.
Have a nice day/night/week/weekend!
Wherever you're far away.
similar and their own superstitions
Yes, you are quite right, every countries have similar and their own superstitions
. We knock on wood and spit out the left shoulder against evil-eye 
. Thank you for the lesson. 
In my country
they "touch Iron"!
It would be interesting to find out why!
Personally I don't touch Iron...but I can be superstitious sometimes.
In my country, especially in the south part they use to raise the forefinger and little finger of the hand, hidden in the pocket.
EL
Superstitions
I'm a little bit superstitious. And, I must confess, I frequently knock on wood, in spite of I'm very religious. I can't help doing this.
Thank you for the lesson.
Touch wood
Yeah! We in Russia also touch wood. I think this is a universal gesture
Superstition - where it come from
Touch wood is an example of a superstition that's true but it IS based on human reason. It's origin is based on the miner's behavior in the past. The galleries of the mining plants were made of wood. The miners knocked on the gallery (wood) to check it. Dry (and good) wood sounds different to wet or rotten wood.
Knock on wood
Hyee...
It's Egypiton hapet in Arabic World