A method used to measure a person's penis size. It is measured by where the skitmark is left on the toilet bowl.
In the front indicates a small penis size, in the middle indicates a medium penis size or good sanitation after using the toilet, and on the back indicates a big penis size.

This method works for mosts toilets, and is considered solid proof.
Jon: "Hey! Bob just got finished taking a shit! He always brags about his big cock, let's check it out once and for all by using the toilet ruler"

Kyle: "MAN! Bob really does have a huge dick! The skitmark is at the very back of the toilet bowl!"
by chillsaster November 15, 2010
Get the The Toilet Ruler mug.