The "Clock" System is an extremely common form of males to communicate to each that a hot girl is in their perimeter. However, this system can also be used by females as well, but is not very common
(Two guys walking and they see a hot girl to their right)
Guy #1-Yo, 3 o'clock.
Guy #2-Now that is what I call a fine piece of machinery.
Guy #1-You like how she didn't even notice we were staring because I was able to use a very handy secret code, The Clock System.