[xeonmc]

Analogy: when you knock on doors, how do you decide what rhythm and duration to use, so that it won’t be mistaken as accidentally hitting the door?

[toast0]

Shave and a haircut is the only option in my knocking decision tree.

[cnity]

Thanks for giving your two bits on the matter.

[throwaway198846]

... What does that mean?

[crazygringo]

https://en.wikipedia.org/wiki/Shave_and_a_Haircut