When one shines a flashlight from the rear of ones ball sack while stretching it out with both hands. Large veins are interstates, small veins are in statehighways.
When my wife wasn't looking I surprised her with a view of my Kentucky Road Map. My friend showed me is cobra, I pulled out my Kentucky Road Map.
By Bibbye
Mexican Road Map
Refers to the appearance of the skin and veins when the scrotal sack is stretched taut