# Who is the one knocking?

If I knock once, you knock twice.
If I'm inside out, you knock thrice.
Past 3 o'clock?
Out of luck.

What am I?

• Welcome to Puzzling! "who" or "what"? Oct 26, 2016 at 11:52
• Definitely Sheldon Cooper from Big Bang Theory :D Oct 26, 2016 at 11:59
• @Techidiot thought about him too! lol Oct 26, 2016 at 12:01
• @Techidiot made me lol, except he will knock 3 set of 3 times with no matter what. even in the middle of the night :P Oct 26, 2016 at 12:01
• Could also be Walter White from Breaking Bad :P Oct 26, 2016 at 13:13

Are you…

If I knock once, you knock twice. If I'm inside out, you knock thrice.

This describes the balls bouncing off each other.

Past 3 o'clock? Out of luck.

If you start the initial swing higher than the 3 o'clock angle it wont work correctly.

• I think this is a good answer. +1 Consider there are 4 balls in the cradle. If the 1st is pulled and left, it will hit the second ball which will knock 3rd ball hence serving If I knock once, you knock twice. For the third ball who is inside the cradle but outside first balls reach, it gets knocked by 2nd ball and then knocks the 4th Ball, which comes back and knocks it again hence serving If I'm inside out, you knock thrice. This one will explain better Cradle Sample Oct 26, 2016 at 12:16

Are you a

Wrestler and I am a referee?

If I knock once, you knock twice.

Not 100% on this but if you get knocked down I start to count with 'knocks' or slaps to the mat

If I'm inside out, you knock thrice.

If you are knocked out, I would knock three times before calling the match

Past 3 o'clock? Out of luck.

If you don't get up after 3 counts, you lose