You know how i know your gay 

The method of telling someone that they are gay.
Making them aware of the signs and tell-tale indications that make another aware of the person in question's homosexuality

Nelson: Dude you know how i know your gay?
Jean: How
Nelson: Because you want me to tuck my dick and nuts back and play chuck norris "fire walker" with you...Fag!

Jean: You know how i know your gay?
Nelson: How? Cause your gay and can tell whos gay in the world?

Nelson: you know how i know your gay?
Jean: How
Nelson: You are Toms number one friend on MYSPACE!

You know how i know your gay by Jean is GAY January 20, 2008

You wanna know how I know your gay?  

used to make someone aware that they are about to be told why they are gay. Used several times in a popular movie starring Steve Carrell called 40 Year Old Virgin

Bob: You wanna know how I know your gay?
Callum: How?
Bob: Because you got a tent when playing rugby in sports lessons . . .

You wanna know how I know your gay? by arsenalman December 15, 2008