Just exactly what is their purpose? They stand with a pole that looks like a linesman's flag without the flag and don't do anything. Are they there just to confirm the ball crosses the line and nothing else?
Furthermore, why are they stood on the same side of the pitch as the linesman? Surely, it would be better to have them on the other side of the goal to the linesman in that half of the pitch. I noticed this last night. If they were on the other side of the goal to the linesman, then last night one of them would have been right next to where Silva was taken out by Boateng. Although saying that, he was well placed to see Boateng take out Micah - not that he did or would do anything.