For example, a batter steps forward as he attempts to hit the ball. He misses, but is out of the crease. He quickly turns back and gets his bat over the line just before the wicket keeper knocks the bails off.
Does it make any difference to the score or game?
Just curious as I'm watching a game and this happened, but the wicket keeper stopped just before he knocked the bails off. I'm wondering why he didn't knock the bails off anyway, just in case?
Edit: and a follow up question to this. If it's not against the rules, what stops the wicket keeper just doing this randomly to waste time or for some other reason?