six to twelve 

6 to 12 is a polite way of referring to an erection. Think of the big hand on a clock, and you'll get the picture.

Man when Jenny gave me a hug the other day Steve, I was afraid I was gonna stab her with my six to twelve.

Yesterday was crazy man, i mean when Jane said "let's go to the movies friday night", I totally went from six to twelve.

six to twelve by NuclearMonkey51 October 17, 2008

six to twelve 

refers to an erection.

has to do with a clock hand going from six to twelve....
an alternative interpretation has to do with an increase in length....6in to 12in (an obvious exaggeration for most, but not all)

"dude, check out that hot girl"
"shit! I just went from six to twelve"

six to twelve by elmo89 September 11, 2009