-perhaps we could come up with a SIGNAL!
-(DOOR SLAMS)
The Big Bang Theory Season 10, Episode 16
The point of a secret knock
is to establish a nonverbal SIGNAL...
The Big Bang Theory Season 1, Episode 16
Cut me in half and I won't be
able to give the SIGNAL.
Game of Thrones Season 2, Episode 9
When Mance gives the SIGNAL
and we hit Castle Black,
Game of Thrones Season 3, Episode 7
My spare glasses are in my bedroom,
on my dresser, next to my bat SIGNAL.
The Big Bang Theory Season 1, Episode 11