What is the fat pad? I’ve seen it mentioned a couple of times, but don’t know what it is.
It’s the skin/fat from the top of your dick to your pubic bone. Push your finger into yourself right above your dick, that is your fat pad. If you had a boner and put the ruler on top to measure, then pressed the end of the ruler into your skin, you would be compressing your fat pad. Most of us press until we see blood, then take a measurement.