Why do snooker players tap their finger just before they take a shot?

Question

Why do snooker players tap their finger just before they take a shot?

Answer 1

I think its for good luck ?

Answer 2

To knock off any excess chalk?

Answer 3

Good Question, I also noticed this. Perhaps it is for good luck. I never tap my finger when i play.

Perhaps its meant to give you more of a precise shot...