Knocking on wood, and the spoken expression "knock on wood" or "touch wood" are used to express a desire to avoid "tempting fate" after making some boast or speaking of one's own death.
The expression is usually used in the hope that a good thing will continue to occur after it has been acknowledged. So, for example, one might say: "The rain looks like it's holding off, touch wood", or "Knock on wood, I'm much better now."
- "The girls sure are being good today."
- "We haven't had a diaper explosion today!"
- "They sure are sleeping great."
- "They absolutely LOVE ______ (fill in blank)."