There are two holes that are both aligned so that one bar (scaffold) will go through both of them without twisting the ear.
They are quite unusual and they look really cool.
You normally have to get both holes pierced at the same time (when I got mine they used the same needle but you don't have to) but I know a guy who got the second one done later and just made sure it would line up.
I have a scaffold piercing - it hurt like buggery! Stupid school rules don't let me wear it though so I have to wear a retainer bar and a LeBrette.