[Nathans_Dad]

Basically we are feeling for a bulge coming out of your inguinal canal.

I'm just an internist but as I recall from med school, your little man nuggets originated in your abdomen. They then descended into your scrotum through a little tunnel called the inguinal canal. It closes up mostly after your testicles go through but it is still a bit of a weak area and hernias tend to occur there when abdominal pressure increases (like when Normy flexes his pecs at the beach).

So, we put our finger into the exit of the inguinal canal and ask you to cough (increasing your intra-abdominal pressure). If we feel a bulge of tissue then you might have an inguinal hernia.